ISSN 1870-9095
LATIN AMERICAN JOURNAL OF PHYSICS EDUCATION www.journal.lapen.org.mx
Volume 3 Number 1 January 2009
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A publication sponsored by Research Center on Applied Science and Advanced Technology of National Polytechnic Institute and the Latin American Physics Education Network
LATIN AMERICAN JOURNAL OF PHYSICS EDUCATION Volume 3, Number 1, January 2009
CONTENTS/CONTENIDO
Papers/Artículos
A research on undergraduate students’ conceptualizations of physics notions related to non-sliding rotational motion, Consuelo Escudero, Marco Antonio Moreira, Concesa Caballero 1-8
History of Science for Science Courses: “Spin” Example from Physics, Nilüfer Didiş and Şakir Erkoç 9-12
Totalizing of the didactic teaching – learning process of physics: an alternative for the development of student, Juan Carlos Ruíz Mendoza 13-18
Huygens’ Principle as Universal Model of Propagation, Peter Enders 19-32
Illuminating physics with gas-filled lamps: Exponent-rules, D. C. Agrawal, V. J. Menon 33-37
Chaotic motion of a bimetallic circular plate, Yong-Gang Wang, Dan Li, Jing Wang 38-44
Fourier heat transfer and the piston speed, V. J. Menon, D. C. Agrawal 45-47
Holes in Hall Effect, Lianxi Ma, Qingli Zhao, Chi Chen 48-51
Experiment showing the motion of a falling object and the influence of air drag, Elmar Bergeler 52-54
Estrategia que favorece la comprensión de problemas y la planificación de su resolución, durante la enseñanza de la Física, Manuel Guillermo Pino Batista, Ignacio Ramírez Ramírez 55-61
La enseñanza de conceptos físicos en secundaria: diseño de secuencias didácticas que incorporan diversos tipos de actividades, R. García Salcedo, Daniel Sánchez 62-67
Estudio cinemático del movimiento de cuerpos que ruedan por un plano inclinado, Silvia Calderón, Pablo Núñez, Salvador Gil 68-71
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contents/contenido
Una revisión sobre ideas previas del concepto de fuerza, César Mora, Diana Herrera 72-86
La cámara digital como instrumento de laboratorio: estudio del tiro oblicuo, Silvia Calderón, Pablo Núñez, Salvador Gil 87-92
Detección y análisis de errores conceptuales en estudiantes de física de nivel universitario utilizando el sistema 4MAT, Mario H. Ramírez Díaz, Guadalupe Ángel González Chávez, Isaías Miranda Viramontes 93-101
La formación inicial docente para profesores de Física de enseñanza media: una reflexión sobre una nueva propuesta de formación, Ossandon, B, Contreras, S., Peters, V., Reyes, M. 102-112
Midiendo velocidades supersónicas utilizando Youtube, Pablo Núñez, Silvia Calderón, Salvador Gil 113-116
La contracción de Lorentz en relatividad especial, C. Zagoya, M. Fernández Guasti 117-120
Una aproximación geométrica a la equivalencia masa-energía en relatividad, Rafael Andrés Alemañ Berenguer 121-126
Capturando la física de los resonadores Helmholtz con la ecuación de ondas acústica, Maricel Matar, Reinaldo Welti 127-134
La compuerta mágica: Descripción de un flujo discrepante en dos globos elásticos interconectados, Luis H. Barbosa, Paco H. Talero 135-139
Segundo Coeficiente Virial para el Helio ... ¿La teoría es diferente de la práctica? Erik Albarrán-Zavala 140-152
La Construcción del Conocimiento como Proceso Activo en la Enseñanza A. Quintana-Nedelcos, J. J. Llovera-González 153-157
Análisis de la Reforma Educativa en la Educación Secundaria en México e implicaciones del nuevo plan de estudios en la materia de Ciencias II Alfonso Cuervo, César Mora, R. García Salcedo 158-166
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contents/contenido
Automatización y caracterización de una planta piloto de desalación de aguas por ósmosis inversa. I Caracterización de las membranas, A.B. Lozano Aviles, R.P. Valerdi Pérez, J.A. García Gamuz y J.A. Ibáñez Mengual 167-176
Conference Report: 4th Congress of the WFPhC Zdenek Kluiber 177-178
Reporte de Conferencia: Primer Congreso Internacional sobre la Enseñanza de la Física Eduardo Montero, César Mora 179-180
Reporte de Conferencia: Reunión Anual de la AAPT-MX 2008 Genaro Zavala, Teresita Marín 181-183
Book Reviews Rafael Andrés Alemañ Berenguer 184-187
Announcements 188-192
LATIN AMERICAN JOURNAL OF PHYSICS EDUCATION
Electronic version of this journal can be downloaded free of charge from the web- resource: http://www.journal.lapen.org.mx
Production and technical support Daniel Sánchez Guzmán [email protected] EDITOR-IN-CHIEF Cesar Mora, Instituto Politécnico Nacional (México) Latin American Journal of Physics Education is indexed in:
INTERNATIONAL ADVISORY COMMITTEE Ann-Marie Pendrill, Göteborgs University (Swenden)
Carl Wenning, Illinois State University (USA) Diane Grayson, Andromeda Science Education (South Africa) David Sokoloff, University of Oregon (USA) Dean Zollman, Kansas State University (USA) Edward Redish, University of Maryland (USA)
Elena Sassi, University of Naples (Italy) Freidrich Herrmann, University of Karlsruhe (Germany) Gordon Aubrecht II, Ohio State University (USA)
Hiroshi Kawakatsu, Kagawa University (Japan) Jorge Barojas Weber, Universidad Nacional Autónoma de México (México) José Zamarro, University of Murcia (Spain) Laurence Viennot, Université Paris 7 (France)
Lillian C. McDermott, University of Washington (USA) EDITORIAL POLICY Marisa Michelini, University of Udine (Italy) Latin American Journal of Physics Marco Antonio Moreira, Universidade Federal do Rio Grande do Sul (Brazil) Education (LAJPE) is a peer-reviewed, Minella Alarcón, UNESCO (France) electronic international journal for the publication of papers of instructional and Pratibha Jolly, University of Delhi (India) cultural aspects of physics. Articles are Priscilla Laws, Dickinson College (USA) chosen to support those involved with Ton Ellermeijer, AMSTEL Institute University of Amsterdam (Netherlands) physics courses from introductory up to Verónica Tricio, University of Burgos (Spain) postgraduate levels. Papers may be comprehensive reviews or Vivien Talisayon, University of the Philippines (Philippines) reports of original investigations that make Zdenek Kluiber, Technical University (Czech Republic) a definitive contribution to existing knowledge. The content must not have been published or accepted for publication elsewhere, and papers must not be under consideration by another journal. EDITORIAL BOARD This journal is published three times Amadeo Sosa, Ministerio de Educación y Cultura Montevideo (Uruguay) yearly (January, May and September), one Zulma Gangoso, Universidad Nacional de Córdoba (Argentina) volume per year by Centro de Investigación en Ciencia Aplicada y Tecnología Deise Miranda, Universidade Federal do Rio de Janeiro (Brasil) Avanzada del Instituto Politécnico Nacional Eduardo Moltó, Instituto Superior Pedagógico José Varona (Cuba) and The Latin American Physics Education Eduardo Montero, Escuela Superior Politécnica del Litoral (Ecuador) Network (LAPEN). Manuscripts should be Josefina Barrera, Universidade do Estado do Amazonas (Brasil) submitted to [email protected] or [email protected] .Further information is Josip Slisko, Benemérita Universidad Autónoma de Puebla (México) provided in the “Instructions to Authors” on Juan Evertsz, Universidad Pontificia Católica Maestra y Maestra, (Rep. www.journal.lapen.org.mx Dominicana) Direct inquiries on editorial policy and Julio Benegas, Universidad Nacional de San Luis (Argentina) the review process to: Cesar Mora, Editor in Chief, CICATA-IPN Av. Legaria 694, Col Leda Roldán, Universidad de Costa Rica (Costa Rica) Irrigación, Del. Miguel Hidalgo, CP 11500 Manuel Reyes, Universidad Pedagógica Experimental Libertador (Venezuela) México D. F. Mauricio Pietrocola Universidad de Sao Paulo (Brasil) Nelson Arias Ávila, Universidad Distrital, Bogotá (Colombia) Copyright © 2007 César Eduardo Mora Ley, Latin American Physics Education Octavio Calzadilla, Universidad de la Habana (Cuba) Network. (www.lapen.org.mx) Ricardo Buzzo Garrao, Pontificia Universidad Católica de Valparaíso (Chile)
ISSN 1870-9095
EDITORIAL
Dear readers,
In this issue we present a collection of papers from Argentina, Brazil, Chile, China, Cuba, Ecuador, India, Mexico, Czech Republic, Turkey and North America, where are studied important topics on students’ conceptualizations on classical mechanics, especially those related to rotational motion, free fall, parabolic shot, and inclined plane. Also, there are different teaching strategies such as teaching physics history, teaching sequences, problem solving, analysis of video, laboratory practices, use of digital cameras and discrepant experiments. It is included an analysis of the educational reform of high school in Mexico and its effect on the teaching of physics. Also we include interesting works about subjects of optics, quantum mechanics, general relativity, thermodynamics, heat transfer, characterization of membranes and mathematical physics.
It is gratifying to report that we achieved our goal of becoming an indexed journal. Now LAJPE is registered in the prestigious databases DOAJ, Latindex and DIALNET. Also, currently we are preparing some additional issues on reports of Physical Education meetings.
On behalf of the editorial board of LAJPE, we want to thank all the authors who made possible this issue and wish you a New Year full of success and happiness.
César Mora Editor in Chief
EDITORIAL
Estimados lectores,
En este nuevo número presentamos una colección de artículos provenientes de Alemania, Argentina, Brasil, Chile, China, Cuba, Ecuador, España, India, México, República Checa, Turquía y Norte América, en donde se estudian temas importantes sobre conceptualizaciones en los alumnos sobre nociones de mecánica clásica, en especial las relacionadas con movimiento rotacional, caída libre, tiro parabólico, plano inclinado y fuerza. Asimismo, se presentan diferentes estrategias de enseñanza tales como el uso de la historia, secuencias didácticas, solución de problemas, análisis de video, prácticas de laboratorio, uso de cámaras digitales, experimentos discrepantes. Se incluye un análisis de la reforma educativa de la escuela secundaria en México y su efecto en la enseñanza de la física. También se incluyen interesantes trabajos sobre temas de óptica, mecánica cuántica, teoría de la relatividad general, termodinámica, transferencia de calor, caracterización de membranas y física-matemática.
Es grato informar que alcanzamos nuestra meta de llegar a ser una revista indexada. Ahora LAJPE está registrada en las prestigiosas bases de datos de DOAJ, Latindex y DIALNET. También, actualmente estamos preparando algunos números suplementarios de memorias de congresos de Enseñanza de la Física.
A nombre del comité editorial de LAJPE queremos agradecer a todos los autores que hicieron posible este número y les deseamos un nuevo año pleno de éxitos y felicidad.
César Mora Editor en Jefe
A research on undergraduate students’ conceptualizations of physics notions related to non-sliding rotational motion
Consuelo Escudero1,2, Marco Antonio Moreira3 y Concesa Caballero 4 1Departamento de Física. Facultad de Ingeniería. UNSJ Avda. Libertador 1109 (O). CP 5400. San Juan. Argentina. 2Departamento de Biología. Facultad de Ciencias Exactas y Naturales. UNSJ Avda. Ignacio de la Roza y Meglioli. Rivadavia. San Juan. Argentina. 3Instituto de Física da UFRGS, Caixa Postal 15051. 91501-970 Porto Alegre, RS, Brasil. 4Depto. Didácticas Específicas, Universidad de Burgos, C/. Villadiego, n/n, 09001 Burgos, España.
E-mail: [email protected]
(Received 14 October 2008; accepted 18 December 2008)
Abstract This paper presents research findings of a study on specific conceptions held by college students in an introductory physics course when they explain a non-sliding rotational motion from the kinematical standpoint, as a uniformly accelerated rectilinear motion, and from the rotational dynamics framework, as well as the role of rotational inertia in this situation. Students’ written answers to a paper and pencil problem are analysed in the light of Vergnaud’s conceptual fields theory. The research was carried out under the qualitative paradigm in which data are grouped in categories which are not previously defined by the theoretical framework. The analysis of the results allowed the identification of some elements of the schemes students would use to handle the task. The findings show the potentiality of such a framework to interpret the construction processes of students’ representations, as well as to design instructional strategies to facilitate critical meaningful learning.
Keywords: students’ representations, operational invariants, reasonings, non-sliding rotational motion.
Resumen En el trabajo se presentan los resultados de una investigación sobre concepciones y competencias específicas en estudiantes universitarios de primer curso acerca de los distintos modos de explicar el “mecanismo” de un movimiento de rodadura sin deslizamiento desde la dinámica rotacional y desde un punto de vista cinemático como movimiento rectilíneo uniformemente acelerado y el rol de la inercia rotacional en el mismo. Las respuestas principalmente a un trabajo escrito sobre rotaciones se analizan a la luz de la teoría de los campos conceptuales de Vergnaud. Es una investigación de tipo cualitativa, donde los datos se agrupan en categorías que no son provistas a priori por el marco teórico. El análisis de resultados permite identificar algunos elementos de los esquemas que usarían los estudiantes para resolver la tarea. Las conclusiones muestran la potencialidad de este marco teórico para interpretar los procesos de construcción de las representaciones de los alumnos, y para la elaboración de propuestas instruccionales tendientes a un aprendizaje significativo crítico.
Palabras claves: representaciones internas, invariantes operatorios, razonamientos, rodadura.
PACS: 01.40.Fk, 01.40.gb, 01.40.Ha ISSN 1870-9095
I. INTRODUCTION problem must have so that certain levels of comprehension are accessible. In a detailed analysis of a problem This study is part of a broader project which aims at situation, one can infer the presence of some implicit searching for tokens that indicate the presence of knowledge, traditionally difficult to be detected, whose operational invariants during the physics problem solving quality and organization influence notably in the process and their relation to mental representations. procedures people undertake trying to solve such problem As the research in problem solving advances, the bonds situation. with the learning of concepts and with the implicit A critical review of the processes and results in relations to meaning in its broadest sense start to line up. problem solving research and the configuration of That is to say, which are the general and particular Vergnaud´s theory of conceptual fields as an alternative conditions one has to rely on in order for learning to exist, theoretical framework for research in problem solving in considering from the context and the environment up to sciences [1, 2] as well as a plausible referent for the minimum requirements which the statement of the integrating the mental models of Johnson-Laird to the Lat. Am. J. Phys. Educ. Vol. 3, No. 1, Jan. 2009 1 http://www.journal.lapen.org.mx
Consuelo Escudero, Marco Antonio Moreira y Concesa Caballero action schemes of Vergnaud [3, 4] have provided some Among the individuals, what is developed are ways of light to interpret research findings of this study. organizing the activity. To develop such notion, Vergnaud Precisely, what makes possible the characterization of used and redefined Piaget’s concept of scheme2. He calls some operational invariants – theorems and concepts in scheme an invariant organization of behavior to a given action – is their use in problem solving. The need emerges, class of situations [5, 6, 9, 10]. It is not the behavior which then, for identification and, therefore, for investigation and is invariant, but its organization. Therefore, a scheme is a documentation of them. Specifically, the problem solving universal which is efficient to a range of situations that in non-sliding rotational motion requires the use of many may generate different sequences of actions, of concepts and their relationship, the comprehension of recollection of information and of control, depending on which presents different levels of difficulty, especially in the characteristics of each particular situation [10]. solving problem-situations that interrelate them. According to Vergnaud [5, 6, 11], the components of the schemes are: -Anticipations of the objective to be achieved, of the II. THEORETICAL FRAMEWORK effects to be expected and of the occasional intermediate stages; Vergnaud’s theory of conceptual fields1 is a -Rules of action such as “if… then” which allow the psychological theory of concepts [5], a cognitive theory of generation of the subject’s sequence of action; that is, rules the process of conceptualization of reality. It is a pragmatic of information search and of control of the results of the theory inasmuch as it presupposes that knowledge actions; acquisition is shaped by situations, problems and actions -Operational invariants (…) which guide the of the subject. It is, therefore, through the situations that a recognition of the elements belonging to the situation and concept acquires meaning to a student. It is, furthermore, the information taking on the situation to be dealt with. a theory of the cognitive complexity, which contemplates These are the knowledge contained in the schemes; the development of progressively dominated situations, of -Possibility of inferences (or reasoning) which allow the concepts and theorems needed to successfully operate “to calculate” – here and now – the rules and anticipations in these situations and of the words and symbols that can from the information and operational invariants which the effectively represent these concepts and operations to the subject has available. individual, according to his/her level of cognition. To Franchi [7] the absence of an appropriate Gérard Vergnaud, Piaget´s disciple, in his theory, conceptualization is at the origin of the systematic enlarges and redirections Piaget’s focus on the general mistakes made by students. However, the operational logic operations, on the general structures of thought, to invariants are the ones that articulate practice to theory, the study of the cognitive functioning of the “subject-in- that is, the ones to make the articulation essential, once the action”. Besides that, differently from Piaget, he assumes perception, the search and the selection of the information as frame of reference the content of knowledge itself and would be based completely on the concepts-in-action the conceptual analysis of the domain of such knowledge system available to the student (objects, attributes, [6, 7]. To Vergnaud, Piaget did not realize how the relations, conditions, circumstances) and on the theorems- cognitive development depends on situations and on in-action subjacent to his/her behavior. specific conceptualizations necessary to deal with them The operational invariants refer to objects, properties [6]. and relations which are kept through a series of situations. Vergnaud considers that a concept is a triplet of sets [8, They determine what belongs, or not, to a specific concept. 5, 7]: C=(S, I, L) where This knowledge, obviously, does not appear as in its S: set of situations which give sense to a concept (the disciplinary formulation – physics, mathematics, etc.- but referent); is used in the action and in the resolution of tasks, I: set of operational invariants associated to the situations, problems. Vergnaud denotes them to show concept (the meaning); their similarity to the corresponding categories of thought L: set of linguistic and non linguistic representations as defined in the light of logic, stressing here its implicit which allow for the symbolic representation of a concept, character: “The operational invariant implies the its attributes, the situation to which it applies and the construction of stable objects of thought which allow the procedures which it nourishes (the significant). construction the subject’s rules of actions” [12]. Vergnaud assigns to the term situation a limited, A theorem-in-action is a proposition considered true though sometimes ample and varied, meaning, the one of upon reality; a concept-in-action is a category of thought task or problem to be solved. To him, the situations are the considered pertinent [9, 10]. ones that give meaning to a concept and the meaning is not On the other side, to Vergnaud, “problem is everything in the situation itself. A concept becomes meaningful to a that, in one way or another, implies, from the student, the subject through a variety of situations and of different construction of an answer or an action which produces a aspects of the same concept which involve such situations. certain effect” [8]. The most important criteria – as for this
1 A comprehensive description of Vergnaud’s theory of conceptual fields 2 This is not a simple concept, for the same word has been used with and its implications to the research and teaching of science can be found many different meanings in cognitive psychology. To this aspect one in [3] and in [2]. may consider its differentiation in [1]. Lat. Am. J. Phys. Educ. Vol. 3, No. 1, Jan. 2009 2 http://www.journal.lapen.org.mx
A research on undergraduate students’ conceptualizations of physics notions related to non-sliding rotational motion expert – is the activity and action in situation, or what In classic cognitive psychology, language is conceived, psychologists denote as "problem solving" with a much above all, as a vehicle for expressing thought, the broader meaning than it has for physicists and representations that an individual has built in his/her mathematicians. The notion of problem contains, relation to the physical world. It is shown here that the therefore, the idea of novelty, of something never done, of language – mathematical, graphical, etc. – of the solver is something still not understood (of a challenge). This does used as a vehicle of meanings (as done in other studies) not mean, however, that the cognitive system through and of inferences made when elaborating a solution. which the subject approaches the new problem is also new, One of the teachers' tasks is seeing that the errors come quite the contrary, it is usually an old system, solidly to light so that they can analyze them and, thus, to detect acquired [8]. This conception of problem opens way, on which are the obstacles to overcome [14]. This means that one side, to an inclusive teaching of physics, and, on the the understanding of the problems of teaching and learning other, to a physics that searches for more meaning [2]. rely at the same time in the analysis of the predicative3 The research on science education, traditionally, has forms and of the operative forms of knowledge. identified problem solving and concept formation as With such studies we intend to value the use of disassociate and differentiated; seeing problem solving, problem-situations. Here, we analyze one, which has the many times, as a new combination of actions and rules objective of characterizing the motion of bodies along a which rely on the knowledge already formed, and the slope, by means of two approaches: from the kinematics elaboration of concepts, as the emerging of new categories, point of view, as a uniformly accelerated rectilinear of new ways of conceptualizing the world, of new objects motion, and from the rotational dynamics standpoint. and of new properties of these objects. Records were taken of the interaction with students in According to Vergnaud, and to our understanding, consulting appointments as well as in moments of group or considering problem solving and concept formation this individual problem solving, as, for example, during and way is a mistake, for it underestimates two aspects: the after course evaluations. This set of techniques: informal symbolic representation and the concepts present in the interview in appointments, field observation and the resolution of problems on one side; and the problem productions of the students, allowed us to obtain a good solving which appear, in concept formation on the other. amount of material, which supplied the data in context. These two elements form the same thing: the The research was carried out in real classroom situation, conceptualization. during the second semester of 2004, in the subject Physics The study of conceptual fields, undertaken in I of the School of Engineering and in Physics I of the mathematics by Vergnaud, may be easily extended to other Licenciatura course in Geology of the Exact, Physics and areas. In physics there are many conceptual fields which Natural Sciences College of the National University of San can not be immediately taught, neither as system of Juan, Argentina. The credit course time – in the first case – concepts nor as isolated concepts. An evolutionary was 10 (ten) hours a week, in a quadrimestral schedule and perspective of learning in these fields is necessary. We with a previous course on calculus, algebra and believe that the topic non-sliding rotational motion may mathematical analysis; while In the Licenciatura course in offer important advances in this direction. Geological Sciences, Physics I is a subject with six hours a In synthesis, the key concepts of the conceptual fields’ week, annual schedule and parallel course in Mathematics theory are, besides the concept of conceptual field itself, I. We analyzed the written resolutions of 41 students of the the concepts of scheme, situation, operational invariant first year of Engineering (during the third evaluation (theorem-in-action and concept-in-action) and the undertaken by the students) and of 16 students of the first conception of concept. year of Geology (during their fourth partial evaluation), As stated before, this theory stresses that the respectively; to the following problem situation: acquisition of knowledge is shaped by the situations and A hollow sphere and a cylinder, both having the same problems previously dominated and that this knowledge mass and radius, set out from rest and roll along the same has, consequently, many contextual characteristics. slope. Which one of them reaches the bottom first? Why? The solution can be expressed by making considerations on energy, or even, on force and torque. III. RESEARCH METHODOLOGY The resolution that sets out from considerations on energy, valuing its conservation, bases the election of the first This is a qualitative, exploratory, kind of research, where body to reach the bottom according to the higher velocity the data is grouped according to categories which are not of the mass center associated to it: foreseen by the theoretical framework. The categories WFNC = ΔEM = 0 ⇒ ΔEPG + ΔEC = 0 emerge from the analysis of the data [13] grouping the ΔEPG = - ΔEC ones that have similar characteristics. This implies an immersion in them which allows to get to know their 3 That is, be able to explicit the objects, concepts and their properties [9]. similarities and differences in such a way as to be able to For instance, the same concept changes the conceptual level when is find a quality that describes them the most accurate appears in a statement as a noun (in this case, it is object of thinking and possible. We have analyzed more the processes than the theme of assertion), or as an adjective, a verb or as a relation (in this case, results, although it is also our interest to know if the it is a predicate) [15]. Expliciting leads to learning to use systems of external representations and its use modifies the structure, according to a students are able to reach a correct result. Vygotskian perspective. Lat. Am. J. Phys. Educ. Vol. 3, No. 1, Jan. 2009 3 http://www.journal.lapen.org.mx
Consuelo Escudero, Marco Antonio Moreira y Concesa Caballero
ΔEPG = -WP = mgh value for basic research and for its implications for a new 2 mgh = ½ IEIR ω = cte ; vCM = wr didactics of physics. t = f (I, ω) Categories have been designed in terms of explicit concepts and operational invariants, that is, in terms of Whereas the resolution that sets out from force and torque which knowledges-in-action are being used. The valuing justifies its election from the identification of the higher of these aspects allowed for the differentiation, in first acceleration taken during the full time. Their answers instance, of five groups of difficulty, which were indicate that the acceleration will relate to the different conceived according to limitations of the physical motion magnitudes through the fundamental equation of the that students perceived and their interpretation from the rotational dynamics explaining that the only force that assumed theoretical framework. produces torque is the weight which acts upon the mass a. Students who considered that the body to reach the center of the body, for the reactions (N and fre) apply upon bottom first is related to that of greater value of inertia. the same rotational axis (contact generatrix). Using the b. Students who identify the dependence of this arrival properties of the instantaneous rotational axis a solution is: exclusively with a greater kinetic energy. a c. Students who operate inferring that at the end the ∑ τEIR = m g senθ r = IEIRα ==I. EIR const speed “v” to the bottom depends only on a numerical r factor obtained from considerations on energy. → t = f (I, a ) CM d. Students who deduct from the fundamental equation
of rotations that the acceleration depends only on the
numerical coefficient. IV. ANALYSIS AND DISCUSSION OF THE e. Students who assume properties and principles RESULTS which, applied to the body, allow for the determination of a winner. In order to be able to solve this problem situation, a As for the first group (a), the kind of difficulties found student needs to understand that both bodies set out appear more distributed and associated to quite elementary together from rest, from the same height of the slope and schemes. Reference to the magnitude “rotational inertia”, roll without sliding. In this case, the rotational axis is though with a meaning reduced to mass as translational predetermined, but it isn’t fixed in space: in each instant inertia and centered in a very deep rooted perceptual there is a different rotational axis, given by the contact aspect: the visual image of a massive body ( in a sense of generatrix; or better, by an axis that passes through the greater volume) at fall. The students seem to present a mass center. The forces that act upon each body are their partial form of explanation centered in the “moment of weight P, the vinculum reaction N and the static friction inertia” as the only variable. 4 force fre, which prevents the point of contact from sliding. Rotational inertia or moment of inertia is a simple To establish the equation of motion we can consider predicate. The students in this group deal with this notion the non-sliding rotational motion as the rotational motion in a very elementary way. The “execution” of this around an axis that passes through the mass center, to movement would be a strong invariant in the construction which the motion of translation of the axis of velocity Vcm of the concept of non-sliding rotational motion, which, is superposed. That is, every point of the body will have a together with new concepts acquired during instruction velocity v = vcm + w x r. The vector w isn't arbitrary: it is (particle, inertia), would supply elements to focus the fixed by the condition through which the points of the attention on the descending movement of a large size generatrix of contact with the slope have null velocity body5. (rolling without sliding) vp = vcm + w x rp. Since rp⊥w, the Despite that, the absence of concepts such as rigid modulus of w ends up as w = vcm/rp. body, rotational inertia, “shape” of the body, rotational This motion can also be considered as pure axis, principle of superposition, instantaneous rotation, instantaneous rotation around the contact generatrix, with among others, prevents from focusing the attention in the same angular velocity w. Notice that in this case, in a critical aspects of the problem situation. In the following posterior dt instant, the rotational axis is other (determined box we have synthetized the knowledge-in-action the by the new contact generatrix), called, therefore, students seem to sustain. instantaneous axis. The velocity of any point is now v = w x r’, where r’ is the position regarding a point of the Concepts-in-action: mass, inertia, speed, particle, external force, rotational axis. To establish the equation of motion it will acceleration. be enough to use again the fundamental equation of the Theorems-in-action: “the faster, the lesser time”, “the body with rotations and its projection upon the contact generatrix is more inertia arrives first”, “the rotational inertia is bigger when the mass of the body moves away from the rotational axis”. enough.
This problem links founding concepts of mechanics and their relations. The use of the error as mark or trace of 4 a genuine intellectual activity, together with its analysis The body (sphere, cylinder, etc.) is the one having moment of inertia. 5 Many people confound mass and volume and/or mass and weight. They allowed us to observe that , besides the elements described think that an object with large mass must have a large volume and/or that in the literature, [16, 17, 18, 19, 20, 21, 22], some students something that has a large amount of matter is very heavy as well. Weight showed certain problems of conceptualization of great is a measure of the force exerted on a body due to gravity. Mass and weight are proportional but not equal. Lat. Am. J. Phys. Educ. Vol. 3, No. 1, Jan. 2009 4 http://www.journal.lapen.org.mx
A research on undergraduate students’ conceptualizations of physics notions related to non-sliding rotational motion The coherence of these mistakes allowed us to information, making it difficult for a scientifically formulate the main theorem-in-action put at play: The acceptable resolution to appear. body with greater inertia6 arrives first. In their Kinetic energy (of rotation) is also a simple predicate. resolution, they used implicit rules of action, theorems and The students characterized in this group employ it in an concepts-in-action which had a local range of validity. elementary way and joined to a perceptual aspect: the These ideas are logical and consistent with everyday visual image of a body of great rotational inertia and, observations. The answers revealed the stability of such therefore, of greater energy converted in kinetic energy of conceptions: rotation. This execution would be another strong invariant in the construction of the concept of non-sliding rotational - “ motion. In a body which rolls along a slope from rest until r Ie diminishing its height in “h”, the variation of potential Ic r energy divides itself between the variation of the rotational and translational kinetic energy. The equality of total m (=) mass, “the greater the rotational inertia, the greater will be r (=) the fraction of energy converted into rotational kinetic energy”. We synthetized the main knowledge-in-action the - The sphere has a greater moment (of inertia), students seem to manifest: therefore it will arrive first at the bottom”. Student 26. Concepts-in-action: speed, lineal velocity, kinetic energy of - “The one to arrive first is the sphere because of rotation, body, incipient rotational inertia, incipient superposition the greater I”. Student 30. principle, sliding. - “The sphere will arrive first because it has Theorems-in-action: “The greater the rotational inertia, the greater will be the energy converted into kinetic energy of greater moment of inertia than the cylinder”. rotation”. “The greater the kinetic energy of rotation, the faster”. Student 10. “The faster, the sooner the arrival”. - “The one with the greater moment of inertia arrives first.” Student 39. The key theorem-in-action seems to be: The greater - “The sphere arrives first because the cylinder rotational inertia, the greater energy converted into takes longer to reach velocity due to lower kinetic energy of rotation, therefore, sooner arrival, moment of inertia”. Student 18. remaining implicit “the greater kinetic energy of rotation, - “The sphere has greater acceleration than the the faster” and “the faster, the sooner”. The absence of cylinder because the sphere has greater I than the concepts such as conservation of the mechanical energy, cylinder. The sphere arrives first”. Student Geo work of a force, static friction force, rotational inertia, 04. rolling condition, would prevent from focusing the attention on the non-sliding rotational motion, resulting in Besides the method of resolution employed, none of the difficulties to explain. That is, in explaining objects, students made a free body diagram. Some made just a concepts and properties: scheme of the physical situation. Most just solved it using considerations on energy. In this case, they prefer to - “The one to arrive first is the sphere since it has conceive the non-sliding rotational motion as a greater kinetic energy at the arrival: Ec e > Ec combination of the center of mass rotational motion and c”. Student 41. the rotation around itself. In exchange, if they employ - “The cylinder arrives first. The cylinder has torque and forces, fundamentally they solve it as pure greater rotational inertia, therefore has greater instantaneous rotation. kinetic energy”. Student 36 (compares inertia). With respect to the second group (b), we distinguish those aspects which allude to the kinetic energy magnitude Student 41 limited himself to comparing kinetic energy at associated mainly to speed and/or velocity (and, in turn, to the bottom of the slope, without relating neither work nor rotational inertia). That is, they show a quite more global gravitational potential energy. form of explanation. As we know, kinetic rotational energy A difference that seemed important to us in relation to is a function of two physics magnitudes: rotational inertia the first group is that we noticed the presence of an and angular velocity, but the students seem to “synthesize incipient notion of “body” different from the notion of “the it” as the only way to explain, without realizing that the particle model” (model which had been being worked with variation of the kinetic energy is the same in both bodies up to here). The frequency of appearance of the second along the considered section. This dependency of the category is quite smaller, though they continue sharing a information related to the conservation of the mechanical scarce work with the operational forms of knowledge. energy was not considered. The absence of such The need for a third group (c) is based in the reference operational invariants allowed the selection of relevant to both magnitudes: rotational inertia and kinetic energy as cause of the type of motion. This mental representation has resulted as more 6 Galileu established that every body presented resistance to change its difficult to characterize, it has depended on the amount of state of motion. The concept of inertia, proposed by him, discredited the aristotelic theory. available operational invariants and on which aspects of Lat. Am. J. Phys. Educ. Vol. 3, No. 1, Jan. 2009 5 http://www.journal.lapen.org.mx
Consuelo Escudero, Marco Antonio Moreira y Concesa Caballero the situation are more significant. Rotational inertia is different rotational inertia around the axis x, y, and z7. The present in a more complete way, although still reduced. knowledge-in-action was summarized as follows: The quality of the invariants was more elaborate. They are centered in the use of considerations on energy (WR = Concepts-in-action: rotational inertia, torque, rigid body, vector, ΔEC or Wfr = ΔEM = 0) to the rolling motion. The vectorial product, acceleration (angular and lineal), instantaneous operational forms are more developed. They could axis of rotation, pure rotation, external forces. conclude, although always linked to the calculated kinetic Theorems-in-action: “The body with greater acceleration arrives first”. “To change the state of rotational motion of a body, the variable v. As it seems, to this group of students, prevails application of a torque is necessary”. “The greater the torque, the an operational action more important which, at not greater the acceleration”. interlacing with the predicate, limits the conceptualization of reality, reaching meaning through simple comparison of The characterization of this category was difficult. It speeds. That is, to each of the rolling objects, they depended strongly on the quantity and quality of varied established the conservation of mechanical energy, the knowledge-in-action put at play and on the aspects of the theorem of work and energy, and they concluded that the situation which were more relevant to them. All of them speed v at the bottom depends, therefore, on a numerical inferred from the external representation systems used8. factor (not expliciting its dependence on more conceptual They were able to conclude, though always recognizing aspects such as the rotational inertia (I) which alludes to that the kinetic variable calculated a is greater to the how the mass is distributed). cylinder than to the sphere depending on the numerical factor, not expliciting the dependency on the rotational - “Wfre = ΔEM = 0 ; -ΔEp = ΔEc ; ..... inertia. That is, from the particular axis over the one which 6 4 it rotates and from the way in which the mass is distributed veh = gh vc = gh 5 ; 3 around the axis of rotation: The cylinder arrives first since it reaches greater final velocity than the sphere”. Student 04 - “∑τ ext EIR = I α ; (.....) aCM e = 3/5g senθ < aCM c = 2/3g senθ - “ WR = ΔEc ; ..... The cylinder arrives first because it has greater vc = √4/3 gh > veh = √ 6/5 gh acceleration”. Student 16 - “∑τ = I α ; (.....) (distinguishes different I to both The final velocity of the CM is greater to the cylinder bodies and compares acceleration) than to the sphere. If both bodies went over the same So the cylinder arrives first because it has greater distance, it implies that the cylinder accelerated more acceleration”. Student 01 than the sphere, that’s why it arrived before the - “As we can see, the acceleration of the mass center of sphere”. Student 17 the cylinder at the bottom of the slope is greater than that of the sphere, therefore, the cylinder will arrive first at the The kinetic approach as uniformly varied rectilinear bottom”. Student 32 motion was revealed by few students. The relation between the acceleration (or the velocity) and the arrival of The consideration of the motion as pure rotation a body to the bottom seems to be implicit. In this last around the instantaneous axis of rotation (IAR) does not answer, other schemes appear in relation to algorithms have to put at play concepts and relations such as: rolling such as: l = ½ aCM t²; vCM = aCM t; l = ½ vCM t. condition, static friction force, work of a force, mechanical A rigorous and systematic interpretation of the energy conservation. To our understanding, their only solutions allowed for the elaboration of a grouping based requirement as a method of solution would impoverish the on the identification of several concepts and theorems-in- gain of the so anxiously expected conceptualization. action in a moderately articulated way: Despite a greater development of the operatory forms of knowledge in the last group, they continue entailing the Concepts-in-action: rotational inertia (incipient), rigid body, rotational inertia weakly. speed, lineal velocity, angular velocity, kinetic energy, In a fifth group (e), the students establish the mechanical energy, potential energy or work, static friction force, fundamental equation of the rotational dynamics and rotational motion, translational motion, superposition principle, obtain an expression for the acceleration (lineal and rolling condition, mechanical energy conservation. Theorems-in-action: “The loss of potential energy is equal to the angular) based on the involved physical magnitudes. They increase in kinetic energy”. “The body with greater velocity all make a free fall diagram. These students assume arrives first”. (complete or incompletely) relevant mechanical properties and principles which, applied to a body, allow to In the fourth group (d), another system of concepts determine a winner. emerges, such as: torque, mass distribution, instantaneous rotational axis, etc. These students presented a more 7 This means that the rotational inertia is a magnitude still more complex developed notion of rotational inertia. In fact, although not than the simple scalar form we have been using in the course and which is mentioning the dependency of the rotational inertia (I), the part of a longer term psychogenetic process. 8 None of the students of this group considered, even in an implicit way, idea that the rotational inertia of a body isn’t necessarily a the concepts of superposition principle and, therefore, of its equivalence fixed quantity appears, despite not having worked with to the explanation of rolling with as pure instantaneous rotation. Lat. Am. J. Phys. Educ. Vol. 3, No. 1, Jan. 2009 6 http://www.journal.lapen.org.mx
A research on undergraduate students’ conceptualizations of physics notions related to non-sliding rotational motion Some answers establish the fundamental equation of difficulties in learning about non-sliding rotational motion the rotational dynamics and obtain an expression for the related to the structure of reasoning which would be used acceleration (angular or lineal), declaring: to solve the task; and, in particular, of the difficulties - “ associated to the understanding of the role of rotational Cylinder sphere inertia and of acceleration of the mass center (or yet, of the
∑ τ = I α 2 velocity of the mass center when they opt for Ie = ⅔ mr considerations on energy) in determining what bodies of Ic = ½ mr2 Στ different forms arrive first at the bottom of the same slope. α = θ θ We are facing knowledge in construction. Neither I rotational inertia nor kinetic energy are alternative The cylinder falls faster9 because it has less moment of conceptions. Nevertheless, we are dealing with inertia, reaching, that way, greater angular acceleration”. methodologies of work based on alternative conceptual Student 28 systems with different knowledge-in-action at its base. The - “Having different moments of inertia, the angular properties and relations of the concepts (rotational inertia, acceleration will be affected. The one of the cylinder will kinetic energy, torque, etc.) come to play from the be greater due to its lower rotational inertia (its particles situations in which the students are involved and will, are more distant from the rotational axis). If the probably, be involved in. Their learning relies in common acceleration of the cylinder is higher, it will take less time sense and is built from it. As meaningful learning occurs, for it to run along the slope”. Student Geo 04 the individual’s mind organizes itself. Generally, we have a simple sequential mental representation in close relation In the light of the records and of the theoretical to the intuition and to the step by step. framework, the following knowledge-in-action may be The most interesting aspect of the conceptual richness identified: of the analysis and of the students’ reasoning was the identification and signification of the dependency and Concepts-in-action: rotational inertia, torque, rigid body, vector, independence of the information. vectorial product, acceleration (angular and linear), shape of a We could notice that in some “organization forms” the body, Vp= 0, Vcm=w r, instantaneous axis of rotation, pure students offered their conclusions relating numbers and not instantaneous rotation, external forces. physics magnitudes. They were not reasoning, despite the Theorems-in-action: “To the same applied torque, the body with important unfolding of operational forms, which are not in less rotational inertia reaches higher acceleration and arrives themselves enough for reaching conceptualization once it first”. “To change the state of rotational motion of a body, the is necessary that they evolve joined to the predicate forms. application of a torque is needed”. It’s fundamental to learn and to teach to reason based on
properties and principles. We notice, thus, how the thinking operations are We verified through this study that the students used analyzed in close relation to the content worked. These different types of significant to specify, precise, represent operations are the main axis of conceptualization. The and communicate invariants. According to Vergnaud, the operational form of the distinct students evolved, as we operational invariants “support” the representation in the have seen – although, sometimes, not articulated with the level of the signifier, while the language and other symbols predicate form. We agree with Vergnaud [6] in that “support” it in the level of the significant. At last, the explanation and symbolization are important ways through meaning of the concepts is in the operational invariants. which we gain or reach cognitive complexity. All of this has important implications to the classroom,
to the formal or non-formal education. Often we, teachers
and researchers, and even education authorities, lose track VI. CONCLUSIONS of the long way it takes to the construction of knowledge, and of the most basic intervention necessary to be done in The resolution of new and partially new problem- a systematic and intentional form, with specific strategies situations requires meanings. To learn is to acquire useful derived from the associated difficulties. information as conceptual tool to facilitate the resolution The resolution of problems has, many times, reduced of such problems. In this study, above all, the concept of its function to a simple instrument of information theorem-in-action was fundamental for the understanding transposition: a straightly technocratic perspective, which of how the resolution of problems has its base in a has left aside all the weight that the scientific culture and conceptual or nearly conceptual representation of reality history have exerted upon the resolutions. Nevertheless, and how it habilitates the analysis of intuition in physics when we study the history of the resolution and of the terms. solved problem, we are impressed by the importance these The analysis of the students’ answers from the factors have had. theoretical framework allowed the interpretation of some This kind of study aims at acting, on one side, as a starting point of reflections and strategies which specially 9 “Falling” faster seem to be like “arriving” first, in the sense of dropping guide the attention to the formal teaching of the content, faster. Although our objective is not to catalog alternative conceptions, increasing the theoretical support for the mediation in the relation between intuitive knowledge and construction of scientific physics education. On the other side, from a greater knowledge is narrow. The latter may find support in the first. Lat. Am. J. Phys. Educ. Vol. 3, No. 1, Jan. 2009 7 http://www.journal.lapen.org.mx
Consuelo Escudero, Marco Antonio Moreira y Concesa Caballero deepening which would allow the identification of some en torno a la didáctica, Perspectivas 26, 195-207 (1996b). medullar difficulties that, in its turn, with the integration of [10] Vergnaud, G., A comprehensive theory of other data, could be object of hypothesis in additional representation for mathematics education, Journal of studies with an important degree of specificity. Mathematical Behavior 17, 167-181 (1998). [11] Vergnaud, G., A trama dos campos conceptuais na construção dos conhecimentos, Revista de GEMPA, Porto ACKNOWLEDGEMENTS Alegre 4, 9-19 (1996a). [12] Ricco, G., Teorías psicológicas del aprendizaje, This work was supported partially by Research Project Temas de Psicopedagogía 6, Buenos Aires: Fundación 21/I529 CICITCA (UNSJ, Argentina). EPPEC 6, 35-58 (1994) [13] Glaser, B. y Strauss, A. L. The discovery of grounded theory: strategies for qualitative research. (Aldine, Chicago, 1967) REFERENCES [14] Moreira, M. A., Reporte final de la VII Conferencia [1] Escudero, C. y Moreira, M. A., La investigación en Interamericana sobre Educación en Física. Canela, Porto resolución de problemas: una visión contemporánea, Alegre, Brasil. (2000) Actas del Programa Internacional de Doctorado en [15] Vergnaud, G., Education: the best part of Piaget's Enseñanza de Ciencias (PIDEC), Vol. 6, Texto de Apoyo heritage, Swiss Journal of Psychology 55, 112-118 Nº 23. Universidad de Burgos (España)/ Universidad (1996c). Federal Rio Grande del Sur (UFRGS, Brasil). (2004) [16] Cudmani, C., Traslación y rotación simultáneas, [2] Escudero, C., Inferencias y modelos mentales: un Revista de Enseñanza de la Física 8, 31-34 (1995) estudio de resolución de problemas acerca de los primeros [17] Cotignola, Mª I.; Rébora, G. y Punte, G., Situaciones contenidos de Física abordados en el aula por estudiantes animadas de rodadura sin deslizamiento, un camino para de nivel medio, Tesis doctoral. Universidad de Burgos integrar conceptos de mecánica, Proceedings VI Inter.- (España) – UFRGS (Brasil). (2005) American Conference on Physics Education, La Falda [3] Moreira, M. A., A teoría dos campos conceituais de (Córdoba, Argentina), 211-216 (1997) Vergnaud, Investigações em Ensino de Ciências 7, (2002) [18] Dhillon, A. S., Individual differences within problem- Site: http://www.if.ufrgs.br/public/ensino/revista.htm. solving strategies used in Physics, Science Education 82, [4] Greca, I. M. y Moreira, M. A., Além da detecção de 379-405 (1998) modelos mentais dos estudantes. Uma proposta [19] Arriasseq, I.; Lester, M. y Stipcich, S., Cuerpo rígido: representacional integradora. Investigações em Ensino de experiencia de laboratorio con material de bajo costo, Ciências 7, (2002). Caderno Catarinense de Ensino de Física 16, 92 (1999) Site: http://www.if.ufrgs.br/public/ensino/revista.htm [20] Costa, S. S. C. y Moreira, M. A., A resolução de [5] Vergnaud. G., La théorie des champs conceptuels, problemas como um tipo especial de aprendizagem Recherches en Didactique des Mathématiques 10, 133-170 significativa, Caderno Catarinense de Ensino de Física 18, (1990). 263-277 (2001). [6] Vergnaud, G., Multiplicative conceptual field: what [21] Escudero, C. y Jaime, E., Elementos para una and why? En: Guershon, H. and Confrey, J. (Eds.), The conceptualización de la noción de cuerpo rígido en la development of multiplicative reasoning in the learning of resolución de un problema integrativo, Memorias XIII mathematics, 41-59. (State University of New York Press, Reunión Nacional de Educación en Física (REF XIII), Río Albany, N. Y, 1994). Cuarto (Córdoba, Argentina), (2003). [7] Franchi, A., Considerações sobre a teoria dos campos [22] Guisasola, J.; Ceberio, M. y Zubimendi, J. L., El conceituais, Em: Alcântara Machado, S. D. et al. papel científico de las hipótesis y los razonamientos de los Educação Matemática: uma introdução, 155-195 (1999). estudiantes universitarios en resolución de problemas en [8] Vergnaud, G., Actividad y conocimiento operatorio. Física, Investigações em Ensino de Ciências 8, (2003). En: Coll, C., Psicología genética y aprendizajes escolares, Site: http://www.if.ufrgs.br/public/ensino/revista.htm. 91-104. (Siglo XXI, Madrid, 1983). [9] Vergnaud, G., Algunas ideas fundamentales de Piaget
Lat. Am. J. Phys. Educ. Vol. 3, No. 1, Jan. 2009 8 http://www.journal.lapen.org.mx
History of Science for Science Courses: “Spin” Example from Physics
Nilüfer Didiş1 and Şakir Erkoç2 1Department of Secondary Science and Mathematics Education, Zonguldak Karaelmas University, 67300, Zonguldak- Turkey. 2Department of Physics, Middle East Technical University, 06531, Ankara- Turkey.
E-mail: [email protected]
(Received 17 December 2008; accepted 16 January 2009)
Abstract In this study, we aim to provide the story of spin concept in historical manner to help students’ construction the idea of spin. Historical discussion of physics provides students both information about content and its nature and methods. For this aim, “Stern- Gerlach Experiment”, and its earlier and later ideas about spin were mentioned. Stern- Gerlach Experiment is the one of the most important experiments which indicates “spin” and “measurement” concepts in quantum mechanics. The controversial ideas about determination of “spin of bounded electrons” and “spin of unbounded electrons” by introducing the analysis of scientific debates in history of physics could provide Physics Educators integrating history of physics into physics lectures.
Keywords: History of Physics, Spin, Stern- Gerlach Experiment.
Resumen En este estudio, tenemos como objetivo proporcionar la historia del concepto de espín de una forma histórica para ayudar a los estudiantes en la construcción de la idea de espín. El debate histórico de la física proporciona a los estudiantes información sobre su contenido, naturaleza y métodos. Para este propósito, se mencionan el "Stern-Gerlach Experimento" y sus ideas más tempranas sobre el espín. El experimento de Stern-Gerlach, es uno de los experimentos más importantes que indica los conceptos de "espín" y "medición" en mecánica cuántica. Las ideas polémicas sobre la determinación de la "rotación de los electrones confinados" y del "espín de los electrones no confinados" al introducir el análisis de debates científicos en la historia de la física se podría proporcionar a los maestros la integración de la historia de la física con la enseñanza de Física en las clases de física.
Palabras clave: Historia de la Física, Espín, Experimento de Stern- Gerlach.
PACS: 01.65.+g, 01.40.E-, 01.40.Ha. ISSN 1870-9095
I. HISTORY OF SCIENCE IN SCIENCE masters students’ interim conceptions, and shows being CLASSES overthrown of ideas by another [2], in other words it provides a “psychological validation” [2]. Science develops gradually with its all domains. During this In last three decades, a group of European physicists development, many concepts and theories may inspire the pointed out that physics has a history, and this history might construction of different concepts and theories at different be useful in physics education as a new perspective [3]. In times. The teaching of concepts with their historical context addition, history and philosophy of science courses have may prevent students’ thinking of science courses as a set of taken part in science teacher education [4]. Heilbron (1983) concepts. It provides students connecting the concepts with explained that the historical discussion of physics could previous concepts, scientists and their lives, social, religious provide information both the content of physics and its and economical factors which affect the development of nature and methods [as cited in 3]. concepts. More specifically, history of science is important In this study, it is aimed to use history of spin concept in for science education because it “motivates students”, physics courses with the debates in its history. Spin is a “allows connections between topics and disciplines of concept of quantum theory. It is one of the fundamental science”, “connects the development of individual thinking concepts of quantum mechanics course at departments of and the development of scientific ideas”, “humanizes the physics, in the universities’ physics curricula. The subject matter”, “promotes comprehension of scientific explanations about spin include mathematical calculations, concepts by tracing their development and refinement”, because mathematics is the only way to express the physical “demonstrates that the science is changeable and mutable”, ideas of quantum theory [5]. For this reason, both nature and “allows to students a richer understanding of scientific expression of spin cause it becomes an abstract and counter- method” [1, 2]. In addition, sequencing approach to a intuitive concept for many students. This abstractness may scientific concept provides students’ progress viewpoints, be dismissed partially with analogy of spin as a turning ball Lat. Am. J. Phys. Educ. Vol. 3, No. 1, Jan. 2009 9 http://www.journal.lapen.org.mx
Nilüfer DİDİŞ & Şakir ERKOÇ in its axis. Although this analogy is a good explanation in I. (HI)STORY OF THE SPIN CONCEPT many ways, quantum theory says that spin of some particles (i.e. electrons) not result of this type of motion [6]. Also, A. Gaining Attention and Motivation analogy is type of model and models do not show all characteristics of the physical reality. For this reason, some Eddington (1928) stated about his electron concept in his missing explanations about abstract concepts on the mind with these words: “When I think of an electron there mathematical expressions may result students’ understanding rises to my mind a hard, red, tiny ball” [as cited in 9]. This of the analogy as total physical reality and concluding “spin statement actually says something about abstract and counter is motion of electron in its axis”. The explanations of two intuitive nature of quantum mechanics. In addition, some teacher candidates about spin as follows: students think that quantum mechanical concepts are strange, One of the (male) 4th grade pre-service physics teachers and it is difficult to imagine them [10]. Although, we have who completed quantum mechanics course defines “spin” is no chance to see the structure of an electron in our daily life, “motion of particles around the atom, moving ahead by successful experiments and mathematical calculations turning, repeating this motion in a continuous way”. Another explain its nature in detail. One of the most important (female) 4th grade pre-service physics teacher says “when I experiments in quantum mechanics about the nature of think of spin, electron is the first thing comes to my mind, it electron was performed in 1922, by Otto Stern and Walter is turning of electron in its axis”. The explanations of the Gerlach. physics teacher candidates show us students need more The “spin” concept for an electron which has great conceptual explanations about this concept. importance in the explanation of atomic spectra [11] was Spin caused debates among scientists both its nature and developed mostly by Pauli, Dirac and Heisenberg between due to this its possibility for unbounded electrons. In the the years 1925-1928 [12]. It is firstly proposed by Uhlenbeck years 1920s, in the period of old quantum mechanics, spin and Goudsmit [13]. Pauli explained that spin was a quantum was studied by many scientists. In addition to mathematical mechanical property and it could not be described classically and analogical explanations of spin concept, it should be [as cited in 14]. mentioned about its contextual development, the ideas of Many particles which have spin produce a magnetic other scientists, experiment results in order to provide field in space due to their spin direction. These particles may meaningful learning of the concept. This also may provide be thought as small magnets. When these particles are passed different point of views to students about the concept. in a magnetic field, they scatter in the magnetic field due to There are some methods, which were defined by the their spin direction [6]. The SGE is a successful experiment different researchers, for teachers to introduce history into which shows the scattering of electrons only in two science classrooms such as reproduction of historical directions, and it is a proof for quantum theory by indication experiments, role plays of historical debates and episodes, of electrons had only two possible spin states. In SGE, silver writing pen portraits of major characters, essays, individual atoms were used. The silver atoms were vaporized and they and group projects, reading and interpretation of original were sent from the pinhole of the oven. The un-polarized papers [1]. beam of silver atoms was collimated before entering the Many writers and science educators recommended inhomogeneous magnetic field produced by the magnets “story line” approach to teach science. Story line approach shown in Figure 1. While the beam of silver atoms passing was developed by Lühl, a science teacher, to teach “atomic through the magnetic field, it undergoes splitting, in other theory” at middle schools, Kieran Egan also developed story words two polarized beam of silver atoms appeared [15]. from approach, and Wandersee’s historical vignettes are Stern and Gerlach received the two lines on the plate. Silver some examples for use of history of science [7]. Also, in atom (Z=47) has single electron in its outer shell and this order to help teaching of a narrow topic, a historical electron is in an “s” orbital. Its intrinsic spin angular experiment can be chosen [8]. In this study, the essay about momentum makes the dominant contribution to the atomic history of spin concept was presented by considering the magnetic moment, by this way orbital and spin magnetic historical experiment which is “Stern-Gerlach Experiment” moments of all the other electrons cancel [16]. (SGE) in the story form. Stinner and Williams [7] mentioned some features of story line approach. These are mainly: mapping out the unifying central ideas, providing students with experiment N The beam of silver related to their everyday world, inventing a story line for atoms highlighting the main idea, ensuring the major ideas, concepts and problems, showing that the concepts are diversely. By considering the aforementioned reasons, the historical essay below in a story form may be used in physics S lectures for students. This is a case for the spin concept including debates in its history.
FIGURE 1. Stern-Gerlach Experiment setup.
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History of Science for Science Courses: “Spin” Example from Physics B. A Debate in the Historical Development of the III. CONCLUSION Concept The SGE established the quantization of intrinsic spin [16, Bohr, Pauli and Mott say, in principle, it is impossible to 21] of electron. In historical context, SGE is a subject of measure the spin components of free electron [11]. This was many analyses and discussions, and it exists in physics because of “the spin degree of freedom characterized the curricula, in the atomic physics, modern physics, and electron only when it is bound in an atom” [17]. Mott and quantum physics courses [22]. This study presented a debate Bohr showed that the magnet used in SGE did not work with about measurability of free electron spin in the early years of electron beams because of “the combined effect of Lorentz quantum theory. Explanation of controversial ideas in history Force and Heisenberg uncertainty principle” [as cited in 18]. of physics may provide students different point of views Pauli had also same idea with Bohr and Mott and he also about concept. This essay may be used in the physics courses thought there were not any device based on the classical (at college/ university level) with different aims such as to particle trajectories, and also no magnetic fields in the motivate students before teaching spin concept, to construct separation of an electron beam by spin, in other words, there conceptual understanding of spin concept on mathematical was nothing which measures the electron’s magnetic expressions or asking the possibility of spin for free moment [as cited in 18]. In conclusion of these three electrons to create discussion environment for inquiry in physicists (Mott, Bohr and Pauli) agreed “the charge of an physics lectures. electron relates to its magnetic moment in such a manner that the separation of the spin components by the magnetic interaction is counteracted by the effect of the Lorentz force REFERENCES on the moving particle” [11]. 1928 is the crucial period for Bohr, because the ideas [1] Matthews, M. R., Science Teaching: The Role of History about measurability of free electron spin appeared in minds and Philosophy of Science (Routledge, New York, 1994). [17]. An alternative experiment to SGE was put forward by Brillouin in these years. He suggested that electrons could be [2] Carson, R. N., Science and ideals of liberal education. In separated by spin “using magnetic gradient forces acting B. J. Fraser & K. G. Tobin (Eds.), International Handbook of along the direction of motion, instead of transversely to it” Science Education (Kluwer Academic Publishers, Great [as cited in 19]. However, Pauli, by the support of Bohr, Britain, 2003), pp.1001-1014. rejected Brillouin’s proposal in the sixth Solvay Conference [3] Bavilacqua, F., & Giannetto, E., The history of physics [as cited in 19]. and European physics education. In B. J. Fraser & K. G. Gallup, Batelaan, and Gay [18], in their study which is Tobin (Eds.), International Handbook of Science Education originated the idea of Brillouin, they showed possibility of (Kluwer Academic Publishers, Great Britain, 2003), observing spin splitting of the electron beams by “using pp.1015-1026. longitudinal magnetic field configuration”. Batelaan [15] [4] Matthews, M. R., The nature of science and science explained the longitudinal configuration as: “magnetic field teaching. In B. J. Fraser & K. G. Tobin (Eds.), International gradient is aligned with the electron beam and spin ‘forward’ Handbook of Science Education (Kluwer Academic and ‘backward’ electrons passing through the magnet are Publishers, Great Britain, 2003), pp. 981-999. separated along the direction of propagation”. In Batelaan’s [5] (Taylor [15] study, quantization axis was selected along the Erkoç, Ş., Fundamentals of Quantum Mechanics & Francis, New York, 2006). symmetry axis of the magnet. [6] Turgut, S., & İpekoğlu, Y., Kuantum fiziğinin garip söylemler,. Bilim ve Teknik, 395(10), 46-49 (2000). C. Discussion [7] Stinner, A., & Williams, H., History and philosophy of science in the science curriculum. In B. J. Fraser & K. G. The possibility or impossibility of using electron beam Tobin (Eds.), International Handbook of Science Education instead of atomic beam in SGE is a debate in history of (Kluwer Academic Publishers, Great Britain, 2003), pp. quantum theory. After the SGE in 1922 with beam of silver 1027-1045. atoms, experiment was tried by different beams of atoms. [8] Kipnis, N., A history of science approach to the nature of Later, SGE was conducted by many physicists using the science: Learning science by rediscovering it. In W. F. atoms which have single electron in outer shell potassium, McComas (Ed.) The Nature of Science in Science Education sodium [20]. In 1927, Phipps and Taylor conducted the SGE (Kluwer Academic Publishers, New York 2002), pp.177- by using “hydrogen” atomic beam instead of silver atomic 196. beam. They also observed the splitting of beam. [9] Mashhadi, A., & Woolnough, B., Insights into students’ understanding of quantum physics: visualizing quantum entities, European Journal of Physics, 20, 511-516 (1999). D. Connection of the Concept with Daily Life [10] Fanaro, M. A. F., & Otero, M. R., Basics quantum Electron spin is important for daily life, especially for the mechanics teaching in secondary school: One conceptual technological applications, for the magnetic devices such as structure based on paths integrals method, Latin American computer hard drives [12]. Journal of Physics Education, 2(2), 103-112 (2008).
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Nilüfer DİDİŞ & Şakir ERKOÇ [11] Garraway, B. M., & Stenholm, S. Observing the spin of [18] Gallup, G. A., Batelaan, H., & Gay, T. J., Quantum a free electron, Physical Review A, 60(1), 63-79, (1999). mechanical analysis of a longitudinal Stern-Gerlach effect, [12] Siegmann, C. H., Spin polarized electrons and Physical Review Letters 86, 4508-4511 (2001). magnetism:Revival of an old topic through technical [19] Batelaan, H., Gay, T. J., & Schwendiman, J. J., Stern- innovations, 2006, available at: http://www- Gerlach effect for electron beams, Physical Review Letters ssrl.slac.stanford.edu/siegmann/ 79, 4517-4521 (1997). [13] Tomonaga, S., The Story of Spin (Chicago Press, [20] Taylor, J. B., Magnetic moments of the alkali metal Chicago, 1997). atoms, Physical Review 20, 576-583 (1926). [14] Ohanian, H. C., What is spin?, American Journal of [21] Platt, D. E., A modern analysis of the Stern-Gerlach Physics 54, 500-505 (1986). experiment, American Journal of Physics 60, 306-308 [15] Batelaan, H., Electrons, Stern-Gerlach magnets and (1992). quantum mechanical propagation, American Journal of [22] Van Huele, J. F., & Stenson, J., Stern-Gerlach Physics 70, 325-331 (2002). experiments: Past, present, and future, Journal of the Utah [16] Erkoç, Ş., & Uzer, T., Atomic and Molecular Physics, Academy of Sciences, Arts and Letters 81, 206-212 (2004). (World Scientific Publishing, Singapore, 1996). [17] Garraway, B. M., & Stenholm, S., Does a flying electron spin? Contemporary Physics 43, 147-160 (2002).
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Totalizing of the didactic teaching – learning process of physics: an alternative for the development of student
Juan Carlos Ruíz Mendoza Facultad de Ciencias Físico Matemáticas de la Universidad Autónoma de Nuevo León, Cd. Universitaria San Nicolás de los Garza Nuevo León CP 66451, México.
E-mail: [email protected]
(Received 19 November 2008, accepted 31 December 2008)
Abstract At present, it is often stated that the development of science and technology opens new perspectives for better understanding and application of knowledge, and to achieve these goals it is necessary a great preparation of human material, however, seen it this way we realize that the formation of modern man has been a consequence of technological progress. From a deep humanistic position, it should be somewhat different; it is required to put men in the first place so that such development is a means for growth. It is the sense of this article to contribute in some way to a better training of young generations.
Keywords: Totalizing conception, education- learning.
Resumen En la actualidad, con frecuencia se expone que el desarrollo de la ciencia y la técnica abre nuevas perspectivas para una mejor comprensión y aplicación de los conocimientos, y para lograr estos objetivos es imprescindible una alta preparación del material humano, sin embargo, visto de esta forma la formación del hombre contemporáneo viene siendo una consecuencia del progreso tecnológico. Desde una profunda posición humanista, debía ser un tanto diferente, se requiere de poner en primer lugar –el hombre. De modo tal que dicho desarrollo sea un medio para su crecimiento. Es el sentido del presente artículo contribuir en alguna medida a una mejor formación de las jóvenes generaciones.
Keywords: Concepción totalizante, educación- aprendizaje.
PACS: 01.40.-d, 01.40gb, 01.40.Ha. ISSN 1870-9095
I. INTRODUCTION diagnostic study at the Autonomous University of Nuevo Leon were found results that match those exposed by The difficulties in teaching and learning of physics are a Castellanos and Grueiro [2], some of the coincident results global problem which has been found by several are listed below: investigations, as well. Lillian C. McDermott (1998) states • The design of teaching and learning is confined to the area that "The results of research on the understanding of physics of the school. by students show that certain misconceptions about the • The teaching privileges the cognitive, intellectual at the world of physics are common to students of different expense of the affective-emotional, so experiential, ethical nationalities, from different socio-cultural and media levels and knowledge and being together. of education and of different ages. There are important • Learning is usually done on an individual missing the evidence about the fact that college students have often the potential of the group. same difficulties and conceptual reasoning that the widely • Learning is identified with the acquisition of knowledge, shared by younger pupils "[1]. habits, skills and attitudes for adaptation to the environment The same situation is observed in the Mexican context, not to transform it. where despite the fact that in recent years have been making • We do not associate the teaching-learning in the context of many efforts to improve this situation, there are still a subject teacher with the development of learning to grow traditional models and rote, despite emerging new proposals ability. which demonstrate the importance that basic science possess For the reasons outlined it is essential to operate changes not in the development of the student. only instrumental in the aspects related to the learning of this In a research conducted by the authors, it was found that science, but also argue new concepts in order to improve its there are difficulties in learning and teaching of physics that teaching. are common to other contexts, for example, conducting a
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Juan Carlos Ruíz Mendoza II. ARGUMENTATION OF THE TOTALIZING of knowledge, which allows the person to pass from the real CONCEPTION DIDACTIC knowledge he possesses, to a more abstract knowledge and to other levels. Transcendence is achieved through a thought In surveys to teachers who teach Physics, the following and a transforming action of reality [5]. results were obtained [3], according to responses from the respondents: The lessons of Physics are developed through the explanation of the content (90%), using active methods B. The link between theory and practice as a pathway for (5%) the develop of the classes is based on spontaneity, the integral study of the physical phenomenon experience, and the memory of how they learned and how their teachers acted (89%), the teaching and learning of The author in his experience for more than 20 years as a physics does not link theory with practice (65%) use of professor has acknowledged that in a lecture, still when it is experimentation in class (5%) use of ICT for teaching a matter of following the logic of scientific investigation, the physics (3%) the process of teaching -learning allows: only physical phenomena are studied frequently in an incomplete educate students (80%), only educate the student (0%) way, since the same alone are only described and explained educate and instruct students (5%). In addition there is a on part of the professor and the students reproduce what is great heterogeneity in the teachers who teach physics: listened or read. engineers of various specialties, doctors, and graduates from On the other hand, it is common to study the theory, then other professions. problems are solved and in the final laboratory practice and It was found through a survey of students, that from a experimentation are developed. The time between one sample of 345 students from the Autonomous University of activity and the other could cause a breakdown in Nuevo Leon of engineering and physics, only 24.5% said understanding the external manifestation of the phenomenon that there is a relationship of physics to life, the rest and its essence. In this research the benefits that own the identified it with the reproduction of what has been learned study of the phenomenon in all its physical integrity were and 75.2% said a narrow conception of learning expressing taken into account, in every teaching activity of 3 hours. that the development of feelings, attitudes and values are To achieve the before mentioned is taken into account the accomplished outside school and in lessons of Physics, one physical phenomena integral way of expressing, that total only learns the art. These results correspond to those set out way states that in its study is very important to take into above, showing the difficulties outlined. account the logic. In that way in the education ambient or in The Didactic totalizing conception presented in this a system of activities its possible to comply with three article is directed to a more transcendent understanding of essential moments that correspond with the stated: the the teaching-learning process of physics. It is based on the observation, to understand how the phenomena manifests, paradigm of systemic structural investigation [4]. This the penetration in its regularities by modeling the phenomena approach considers the whole constitutes a dialectical unity and the verification through the experimental activity. of its components and that the properties of the system are What is expressed before can be summarized in the next qualitatively different from the properties of these scheme. components separately are synthesis of the relations between the components or subsystems of all, characterizing the SCHEME 1. Interrelation of the ways and moments of system and its development. learning the physical phenomena. The features of the structural systemic method helped identifying all the group of elements which are components Manifestation of the Observation of reality of the design, and the relationship of significance within the physical phenomenon (external manifestation) different subsystems that integrate it. These relationships of significance in the case of this study are not of hierarchy and subordination, but rather of interaction, provide coherence to Virtual modeling of the the system components. phenomenon (An approach to The essential budgets of the theoretical and Software uses the internal demonstration ) methodological concept hold are as follows:
Verification of the result (A comprehensive A. The transcendent character which the teaching and Experimental research learning process must possess understanding of the phenomenon)
At present, in light of new transformations that take place in the learning process for students, it is important the enhancement of the teaching act. The author of this C. The unity of education and instruction for the investigation starts in the transcendent character that the development of the student teaching process must possess, understanding transcendent as the essential quality required to hold the teaching-learning If the study of a particular area is not developed from a process, which goes beyond the study of a particular branch training approach, nowadays it makes little sense. In
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Totalizing of the didactic teaching – learning process of physics: an alternative for the development of student conjunction with the acquisition of knowledge, skills and education. Is due to reveal in a explicit way to students the habits of each subject it is necessary to develop an active and meanings of values, its systemic nature, guide them in the transforming position and of students toward life, for this it identification of values, since they must know how to is require to direct attention to those areas of the personality respond and not to everything that comes from abroad in that found its realization in all spheres of human activity. terms of fashion, prejudice and views. Discuss with the If we combine the consideration of the physics students about to assume responsibility is not fulfilling characteristics as the science of nature with all the potential certain duties, is to capture the values it embodies, its offered by its teaching and learning process (that is not any meaning and relevance. process) we can determine some guidelines for the training It is about taking advantage of all the possibilities of Physics desired: as a science, as well to the didactic process as a relational A good education is one that exceeds the limits of a and communicative process to be able to influence in a more subject of a science, a field of knowledge [6]. The principle significant formation that is not limited to work for the of unity of instructional and educational based on the assimilation of meaning through the Physics conceptual cognitive-affective aspects, is the key to the appropriation of system. The process of study of Physics, its extensive the modes of action that students acquire their relations applications, the relationship with life, the possibility for the under the aegis of the teacher. Proper linkage of the content development of interpretation, explanation and argument of education with the interests, emotions, feelings that for the (that has a application in all human spheres of student’s cognoscente have meaning, promotes and enhances the development), allows that this discipline can take a positive development of the integrated personality. meaning, that is motivational and educational for the By promoting a proper self-esteem and confidence in students. himself in students, among countless ways, this is possible The results of the diagnostic study, the analysis of the through the structuring of the teaching-learning process not theoretical sources and the author experience, permitted to only focused on the task, but with emphasis on students, support a conception based on a systematic focus where the because not all have the same possibilities. On many integral formation as a system of greater order integrates occasions, there are classes of Physics Students with low other systems, at the same time these are composed by academic performance, which may be a cause of low self- components that are interrelated among itself. Next the esteem. interrelationship between each one are explained (Fig. 1). It is also important to consider for achieving the unity of instructional and educational impact that has values
FIGURA 1. Subsystems and components for the design didactic all-round education for students through the process of teaching and learning of Physics.
The system design that classifies the teaching totalizing methodology, the cultural education and training as a (Annex 1) consists of the subsystems conceptual training synthesis of the two previous ones, are dynamic by the
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Juan Carlos Ruíz Mendoza fundamental contradiction that directs the current methods and means of each item that integrate the different investigation, which is established between the construction programs, which despite possessing specific characteristics of meanings and manifested between the epistemological have a sense of belonging to the conceptual general physical sense of physics and its connotation in the personal and the system. social [7]. The appropriation of knowledge must take place in a dialectical unity with the domain of procedures and strategies for learning, in a way that is conducive to the III. III. ANALYSIS OF COMPONENTS AND development of levels of consciousness, where the SUBSYSTEMS conceptual system acquires a personal sense for the student, in addition to understand its significance for social The training methodology is conceptually related to the development. In the educational practice has not been able to acquisition of knowledge, habits, skills and abilities that the overcome the so-called "transfer of knowledge" based on a student will acquire through the study of the various courses formal explanatory logic, which prevents the teaching- of physics at the middle level, in conjunction with the learning process to postule an epistemology that allows for dominance of the conceptual apparatus the student must be the seizure and in for reality. appropriating the methods, means and procedures of this In this subsystem is very important to encourage an science and that in turn can be transferred to the study of investigative process which the unity between the other branches of knowledge [8]. theoretical, the conceptual is developed, the ways to achieve Cultural formation is one that relates to the acquisition this and checking if it is useful in practice. The research of the experience accumulated by humanity in different tasks that are available to students develop the flexibility of orders that allows the student to interpret and transform thinking, their creative abilities, prepares them to transform reality through the study of physics and its relationship to reality. life [9]. On many occasions troubleshooting is so mechanical that The integral training constitutes the synthesis of the a student can solve a problem correctly from the quantitative, methodological and conceptual training cultural formation but does not know to explain the essence of physical that has its manifestation in a student's preparation in phenomenon, the laws or categories that sustain it [12]. To correspondence with the individual and social needs [10]. achieve a proper relationship between meanings and senses, It argued previously has an enormous value for the didactic it is essential the unity of theory with practice. To do this, it process, indicates the importance to create the spaces for the is not sufficient to substantiate an experiment by the construction of the meanings and senses in narrow relation phenomenon and physical laws, nor the conduct of scientific because before specific conditions, the not coincidence work; it is needed in every moment of teaching, from its own among them can give them a truly alien character and even dynamic to take this fact into account so this will achieve the of mutual comparison, for example when he is capable of necessary flexibility in the student. If this flexibility is not resolving well a problem but not the importance of an achieved, then students can not shed the preconceptions they adequate comprehension can be explained And resolution. have. The matching between the meaning and senses that is In the manifestation of physical phenomenon in nature oriented and linked to the humanization of the learning- and the potential of the teaching-learning process, there is a teaching process when takes into account the student as the contradiction, because when students observed a physical most important element helps in its integral formation, phenomenon can have a distorted perception or incomplete, together with his cognitive development. even though the observation is properly planned, however , One of the contradictions that are manifested in the In the teaching-learning process there are all possibilities to teaching-learning process, is between the social requirements study the phenomenon in its external manifestation, but also that requires people active, creative, transformative people to know the why of this event, its causes, often this potential and reproductive learning of physics, this learning is in is not taken in advantage. contradiction with the reproductive characteristics of an The second subsystem related to the cultural education is apprenticeship training [11]. integrated by the components: gnoseologic logic of physics The subsystems are composed of components also in and the integrated interpretative logic, dinamised by the interrelation with each other. Here are the interrelationships relationship of physics with life. between each one. The first subsystem, related to the The first component: the gnoseologic logic of physics is conceptual methodology training is composed of conceptual needed as a theoretical construct related to the specific components: the physical conceptual system and the specific characteristics of this science that indicate how the physical physics content, which energizes the whole-part relationship. phenomenon should be studied and systematized from The first component: the physical conceptual system is general principles and laws. determined by the system of knowledge, skills, work The second component: the integrated interpretative logic strategies of the subject, methods and means for learning, is related to that theoretical construct that indicates the fact including in the different programs of higher average level that the significant observations did not appear without that identify themselves as a whole. generalized knowledge. The interpretive process as part of The second component related to the specific physical that logic studies the movement from all to the parts and content is identified with the system of knowledge, skills, from the parts to all. For the study of physics from this
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Totalizing of the didactic teaching – learning process of physics: an alternative for the development of student interpretative logic, the unity of the process of observation If there is a proper linking between theory and practice and interpretation could be understood. we get flexibility to understand the reality that goes beyond The logic gnoseologic of physics states that for the the verification of facts and events, such flexibility is what understanding of its conceptual apparatus, it is imperative to allows transcendence axiological, social processes for take into consideration a range of activities, processes and example, require a flexible and open minded. The didactic methods, such as monitoring, modeling, testing, among flexibility has to be manifested on the possibility that the others. For example, teaching to observe is equal to student is free at some point, to propose alternatives, so this conscience awake to the multiple meanings of the way students and teachers harmonize so the teacher stops environment. It involves fixing the attention, applying an being the absolute protagonist. interpretative logic that integrates the discrimination of The third subsystem, related training, which is the elements, their interrelationships and their interpretation synthesis of the previous two components has the potential from them, from this perspective can be seen by the student of Physics and the potential of teaching and learning process as a literary text, a mathematical problem, a physical and stimulate the relationship Science and Physical Science- phenomenon, a social situation or a work of art. The Didactics. interpretative logic allows the student to interpret the world The significance ranging from the unity of meanings and around him as a whole from different forms and methods of senses favors axiological addition to the cognitive aspect, is knowledge that are unique of the gnoseologic characteristics characterized by what look different as established by the of Physics. flexibility of thinking. "The significance is achieved through The demonstration between theory and practice thinking and action of transforming reality, including the constitutes the dynamic element of this subsystem because it subject" [14]. When the student not only plays, but requires a certain flexibility in order to understand the reality understands and questioned, analyzed, certainly appreciates which causes a significant axiological. is shaped in the same axiological aspect. In this case, if the The gneseologic characteristics of physics constitute an teaching-learning process of physics is concentrated only in inexhaustible potential for development of the student, but the student learns his conceptual apparatus, without finding they gain a true sense when applied not only in the field of their way, then it is a training partial, incomplete, not physics but also to the understanding, explanation and transcendent. reasoning of other phenomenon of nature and society. The The publications of Álvarez, et al., [15] about the integral very nature of this science enables the development of the formation of the student help to understand that the didactic argument and interpretation on the students, relying on facts, science, since its own object can favor the necessary spaces concepts and theories, using the right information, assessing for the construction of the meanings unit and the senses in the advantages and disadvantages, contrasting views on the students. If this relation doesn’t become aware on part of improvements and problems that occur in the applications of the professors or its disciples, you can not achieve a Physics. For example, the use of different energy sources for formation that transcends the borders of any of the school obtaining electricity, the use of radioactive isotopes, the use subjects among them of course the Physics. of nuclear energy in this manner he is capable of linking The problem of the scientific content has been scientific, technological, economic and social issues. This sufficiently taken in the didactic and pedagogical literature, explains why when we interpret the physical phenomenon; [16] its reaching and place in the formative process of the this ability can be transferred to other phenomenon and other students. When the learning of a discipline is privileged areas of performance and knowledge. without the student having clarity of the why and what for When studying physics and it is understood by students, this studies are, an incomplete fragmented knowledge is it propagates in them a transforming thought of reality, obtained, if then one agree that "knowledge is action" and to therefore, not only is it possible to develop logical thinking this we should add an action but of ethical content, also skills, build a conceptual change in students, but also their oriented to the social and individual improvement. When it culture can be extended. Moreover, the history of physics, its refers to the need of promoting the formative aspect we want development expressed in different paradigms, broadens the to say that the process of study of any educational discipline student's cultural knowledge, familiarity with the lives of should be a way to prepare the student for life and this great physicists, their attitudes copies, allowing help to objective surpasses way beyond the limits of any particular enrich the look axiological. These potentials of Physics, in knowledge. practice are minimized, because teachers in many cases are Very often we talk about axiological, but separate from permeated by the idea that their role is to make students what the student learns in one subject, in its characteristic “learn physics” therefore it is not seen as a source for the epistemological, if we do not found meaning in something acquisition of culture. that is studied, then the meaning is lost. On the other hand, if Many years ago a very clear Erwin Schrödinger pointed there is meaning and lacks direction, then there is no human out the relationship of science and culture, in this connection growth. That's why these two aspects from the didactic form, expressed "the tendency to forget that science is linked to as has been stated, one unit. human culture in general, and that the scientific findings, From the arguments put forward the concept is defined as like those that in a moment appear to be the most advanced, being didactic totalizing allows encourage the development esoteric and difficult to grasp, lose their meaning outside any of the student through the process of teaching and learning of cultural context "(quoted by Roger Stuewer) [13]. physics from the interplay between the conceptual and
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Juan Carlos Ruíz Mendoza methodological training cultural training with the use of [5] Ruiz, J. C., Formación integral del estudiante mediante methodologies that enable the creation of spaces for the la dinámica totalizadora del proceso de enseñanza construction of meaning and direction so as to achieve a aprendizaje de la Física. Revista cubana de Educación unity between the epistemology of physics and its Superior XXVII, mayo-ago. (2007). connotation in the personal and the social. [6] Torres, A., Un modelo pedagógico para la autotrasformación integral del estudiante universitario Tendencias pedagógicas, Nº 11, (Ejemplar dedicado a: 1V. CONCLUSIONS Teorías, enfoques y políticas de la educación), pp. 155-168, España, (2006). Different studies show that the students present shortages in [7] Ruiz, J. C., Alternative methodology for the training of their formation, the ones that particularly manifest in the students from the teaching-learning process of physics. learning-teaching process of Physics. These shortages are Report doctoral thesis in Education, p. 66, (Universidad de shown in different orders: in the conceptual formation of Camagüey, Cuba, 2005). Physics, scarce development for the explanation, observation [8] Ruiz, J. C., Alternative methodology for the training of and interpretation of the physical phenomena, the little students from the teaching-learning process of physics. preparation for the collaborative work, the inability to relate Report doctoral thesis in Education, p. 53, (Universidad de Physics with life and therefore to understand the importance Camagüey, Cuba, 2005). that possesses for the development of the human being in the [9] Ruiz, J. C., Formación integral del estudiante mediante physical World that we live in. la dinámica totalizadora del proceso de enseñanza In spite of the research related with the learning-teaching aprendizaje. Revista Cubana de Educación Superior XXVII, of Physics it is a challenge for the improvement of teaching pp. 33-43, mayo- ago. (2007). Physics to promote the study of potentialities that this [10] Torres, A., Un modelo pedagógico para la science possess, since its conceptual system and the methods autotrasformación integral del estudiante universitario for its study, that at the same time can be teach and Tendencias pedagógicas Nº 11, (Ejemplar dedicado a: assimilated not only in function of its learning, but with a Teorías, enfoques y políticas de la educación), 155-168 reach that transcends to other spheres of the student, in this (2006). way the gnoseologic takes sense by means of the axiological [11] Ruiz, J. C., Formación integral del estudiante mediante and vice versa. la dinámica totalizadora del proceso de enseñanza aprendizaje d e la Física. Revista Cubana de Educación Superior XXVII, pp. 33-43 mayo- ago. (2007). REFERENCES [12] Fuentes, G., Pérez, L., Mestre, U., Organización del Proceso Docente Educativo en la Disciplina Física General [1] McDermott, L C., Community of learners and problem a través del sistema de Unidades de Estudio, (Ed. solving in mechanics, in: Results of Research in Teaching of Universidad de Oriente, Santiago de Cuba, 1991). Physics in Teacher Training. (ICPE, 1997). [13] Stuewer, R., History and Physical Outcomes Research [2] Castellanos, D. and Grueiro, I., Can the teacher a in Teaching of Physics at the Teacher Training Outcomes facilitator? A reflection on the intelligence and its Research in Teaching of Physics in Teacher Training, (ICPE, development, (IPLAC-CeSofte, Cuba, 1996). p. 8, 1997). [3] Ruiz, J. C., Alternative methodology for the training of [14] Torres, A., Self-education strategy for the integrated students from the teaching-learning process of physics. college student based on a model of transcendence Report doctoral thesis in Education, p. 34. (Universidad de axiological. Thesis Ph.D. in Education p. 35, (Universidad Camagüey, Cuba, 2005). de Camagüey Cuba, 2006). [4] Bertalanffy, L., Teoría General de Sistemas, (Editorial [15] Álvarez, A., Cardoso, R., Moreno, T., Hacia la Herder. Barcelona, España, 1987). Fuentes, G., Matos, H., formación integral del estudiante universitario. Revista Cruz, B., El proceso de investigación científica desde un cubana de Educación Superior 21, 81-90 (2001). pensamiento dialéctico hermenéutico. Homero. Universidad [16] Álvarez, A., Hacia una Pedagogía de los valores de la de Oriente. Centro de Estudio de educación superior Educación Superior Tendencias pedagógicas Nº 6, “Manuel F. Gran”, (en proceso de edición), Santiago de (Ejemplar dedicado a: Didáctica Universitaria), pp. 39-54 Cuba, (2004). (2001).
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Huygens’ Principle as Universal Model of Propagation
Peter Enders Ahornallee 11, D-15754 Senzig, Germany.
E-mail: [email protected]
(Received 2 December 2008; accepted 12 January 2009)
Abstract Huygens’ Principle (HP) contains both the principle of action-at-proximity and the superposition principle. Although the propagation of sharp, non-spreading wave fronts is included in Huygens’ (1690) original formulation, it can be left out without touching those principles. The formulation of HP by means of the Chapman-Kolmogorov equation (following Feynman 1948) comprises both versions and overcomes misunderstandings like ”Huygens’ principle is not exactly obeyed in Optics” (Feynman 1948) and ”HP is incompatible with Green’s functions” (Johns 1974). This way, HP applies not only to the propagation of light, but also to heat and matter diffusion, Schroedinger matter waves, ie, to virtually all propagation phenomena, which can be described through explicit linear differential and difference equations, respectively. HP for Maxwell’s equations is discussed in terms of the Helmholtz-decomposed fields and currents. The appearances of HP in mechanics and in fractional Fourier transformation being exploited in optics are also mentioned.
Keyword: Optics, Huygens Principle, light propagation.
Resumen El Principio de Huygens (PH) contiene tanto al principio de acción a proximidad como al principio de superposición, Aunque la propagación del pico no esparcido de los frentes de onda está incluído en el trabajo de Huygens (1690) acerca de la ecuación de Chapman-Kolmogorov (que sigue al trabajo de Feymann de 1948), incluye a ambas versiones y sobrepasa a los malentendidos como los de que “El principio de Huygens no es exactamente obedecido en óptica” (Feymann 1948) y “PH es incompatible con las funciones de Green” (Johns 1974). De esta forma, el PH se aplica no solamente en la propagación de la luz, pero también en la difusión del calor y la materia, en las ondas de Schrodinger de materia, es decir, a virtualmente toda la fenomenología de la propagación, la cual puede ser descrita a través de ecuaciones diferenciales lineales explícitas, respectivamente. El PH para las ecuaciones de Maxwell es discutido en términos de la descomposición de los campos y corrientes. En este trabajo mencionamos como es que la aparición del PH en mecánica y en las transformadas fraccionales de Fourier está siendo explotada en el campo de la óptica.
Palabras clave: Óptica principio de Huygens’ propagación de la luz.
PACS: 11.10.-z, 41.85.-p, 42.15.-i, 42.15.Dp ISSN 1870-9095
I. INTRODUCTION approximately for optics, and Scharf (1994) stated, that HP is a principle of geometrical optics, not of wave optics. On No one doubts that physics is an exact science. the contrary, the unifying power of HP will be Nevertheless, the notion ’exact science’ “should not be demonstrated here. interchanged with ’like mathematics’. As stressed by Some of that confusion is related to Kirchhoff’s Huygens (1990, p. IIIf.), within physics, “one will find formula and reaches up to doubts on the validity of HP at proofs of a kind, which do not grant the same great all (Miller 1991), or on the possibility of the representation certainness of that of geometry and which even are rather of HP by means of Green’s functions (GF) (Johns 1974). different from those, because here, the principles are Both doubts contradict any mind believing in the unity of verified by the conclusions drawn from them, while the physics. Indeed, Kirchhoff’s solution to the wave equation, geometricians proof their theorems out of sure and while being mathematically exact, suffers from the unquestionable principles; the nature of the subjects dealt drawback of requiring the knowledge of both the field with conditions this”. amplitude and its gradient on the boundaries. I will trace Huygens’ ideas on how light propagates have become the origin of these mathematical and physical difficulties to basic ingredients of our physical picture of the world. The the notions of degrees of freedom of motion and of notion Huygens’ principle (HP), however, is not uniquely independent dynamical variables. used. This paper aims, on the one hand, at the clarification For the sake of the unity of physics, a further goal of of some confusion existing in the literature, in particular, this paper is to generalize Huygens’ basic ideas. This about the role of sharp, non-spreading wave fronts and the means, that I will keep essentially the imagination, that range of applicability. For instance, Feynman (1948) each locus of a wave excites the local matter which wrote, that HP holds exactly for wave mechanics, but only reradiates a secondary wavelets, and all wavelets Lat. Am. J. Phys. Educ. Vol. 3, No. 1, Jan. 2009 19 http://www.journal.lapen.org.mx
Peter Enders superpose to a new, resulting wave (the envelope of those Christopoulos 1995, de Cogan 1998, de Cogan et al 2005). wavelets), and so on. Huygens’ ad-hoc omission of Because here – in contrast to other cellular automata backward radiation as well as Fresnel’s and other auxiliary algorithms (Chopard & Droz 1998) –, an (idealized) assumptions (cf. physical system is mapped, it is not too surprizing that HP Longhurst 1973, §10-2) is requested to be included in a applies to the TLM equations, too (Hoefer 1991, Enders natural manner. In particular, attention will be paid to a 2001, Enders & Vanneste 2003). Therefore, some simple, but general and exact description of wave and implications of our approach to HP for practical, in other propagation processes, which obey the principle of particular, wave-optical computations will also be action-by-proximity and can be described by explicit discussed. transport equations. For historical and methodological reasons, I start in Shortly, consider a complete set of independent Section 2 with HP in mechanics and continue, in Section 3, dynamical variables of a given problem, , with Kirchhoff’s formula and certain problems of its physical interpretation. Then, Hadamard’s rigorous , ,…, , , eg, , , , , / definition of HP is discussed. In section 5, the , , being the amplitude of a scalar wave. I seek to superposition of secondary wave (let)s is represented and represent its propagation in the most simple form illustrated by means of general field propagators in the space-time domain. This leads to a description of wave , , ; , · , ; (1) motion, that overcomes the difficulties in the interpretation and application of Kirchhoff’s formula mentioned above. The “Huygens propagator”, , obviously, obeys the Section 6 stresses the role of time-derivatives of dynamical CHAPMAN-KOLMOGOROV equation variables as independent dynamical variables. When (KOLMOGOROV 1931, 1933, CHAMPMAN & equations of 2nd order in time, such as the wave eqation, COWLING 1939) known from (but not restricted to) are rewritten as systems of equations of 1st order in time, MARKOV processes and related problems of probability HP applies exactly to those and, consequently, to wave theory. optics as well. Section 7 discusses Maxwell’s equations in the light of these results, where the fields and currents are Helmholtz-decomposed, in order to work with independent , ; , , ; , · , ; , ; field variables only. Section 8 applies these thoughts to (2) difference equations and discusses implications for practical computations. A relationship to the fractional Thus, following Feynman (1948), I will express HP Fourier transformation is sketched in section 9. Section 10 through this equation. The rigorous treatment requires condenses these results into thesis for the general measure theory (Dynkin 1965), but this is much more than formulation of the physics of propagation. Sections 11, necessary for the understanding of ’common’ physical finally, summarizes and concludes the results. propagation processes. It may proven useful, however, for the fractal description of wave propagation in disordered media (West 1992) and the like. II. HUYGEN’S PRINCIPLE IN MECHANICS If , obeys a set of partial differential equation of first order in time, , ; , turns out to be the GF of A.Principle for the free fall that equation, and Eq.(1) is the solution to the initial- boundary value problem. If, however, , obeys a set As a matter of fact, the principle of superposition has first of partial differential equation of second (or higher) order been formulated by Huygens for mechanical motions. in time, no such simple equation exists. Often, the much Shortly, during free fall, the momentually achieved more involved Kirchhoff’s formula (11) is used. This has increments of speed add to the speed assumed just before misled some authors to deny a relationship between GF, (Horologium oscillatorium, 1673; after Simonyi, 1990, HP and wave propagation at all. p.241f.). This implies the differentiability of the velocity: The use of GF within such considerations is not new, , therefore, the smoothness of the of course (Courant et al 1928, Spitzer 1964, Keilson 1965). trajectories. However, our goal is the representation of HP through GF rather than a discussion of the probabilistic questions behind such approaches. These are interesting enough, but B.Huygens’ construction for the classical harmonic need (and deserve!) a separate treatment. We will oscilator encounter discrete Markov processes when discussing computational algorithms realizing HP in discrete form. The trajectory, , of an 1D harmonic oscillator can be Such forms are required for numerical calculations on described as function of the initial values of location, 0 , digital computers. The natural formulation is in terms of and momentum, 0 , and of its mass, , and angular Markov chains. On the basis of transmission-line velocity, . networks, powerful algorithms have been developed not only for electromagnetic problems, but also for diffusion 0 (3) and even for mechanical problems (Hoefer & So 1991,
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Huygens’ Principle as Universal Model of Propagation Here, the internal , und external parameters The factorization of that equation is obvious, as 0 , 0 occur in mixed form. Since, generally . speaking, separations highlight the actual physical It is noteworthy that this result was possible only by interrelations, it is desirable to separate internal und external parameters, , in the case, the constants (laws of means of the imaginary unit, √ 1.. This provides motion, system parameters) from the variable influences with a physical (and not only mathematical-calculational) (initial conditions), (WIGNER 1963). justification already within classical mechanics The separation makes it immediately, if one writes (SCHROEDINGER 1926 hesitated to exploit for the down the coupled solutions for both dynamical variables, formulation of the first-order time-dependent and : SCHROEDINGER equation).