DOCSLIB.ORG

Reflection and Refraction

Total Page：16

File Type：pdf, Size：1020Kb

Download full-text PDF Read full-text
Reflection and Refraction Fi Reflection and A thi Refraction wa en at th los Th hen you shine a beam of light on a mir- ref rot the light doesn't travel through the dii Wmurmur. but a returned by the mirror's mutate bact into the ad Aben sound aases strike a canyon wall. they return to you as an echo. When a transverse wave transmitted along Changes tn lasaht speed produce a spring reaches a wall. it rrverNes direction In all these situations. refraction. waves remain in one medium rather than enter a new medium. These waves are reflected. In other situations, as when light passes from air into water, waves travel from one medium into another. When waves strike the surface of a medium at an angle, their direction changes as they enter the second medium. These waves are refracted. This is evident when a pencil in a glass of water appears to be bent. Usually waves are partly reflected and partly refracted when they wa fall on a transparent medium. When light shines on water, for exam- refl ple, some of the light is reflected and some is refracted. To under- pet stand this, let's see how reflection occurs. refl dic the 29.1 Reflection When a wave reaches a boundary between two media, some or all of the wave bounces back into the first medium. This is reflection. 21 For example, suppose you fasten a spring to a wall and send a pulse along the spring's length (Figure 29.1). The wall is a very rigid In medium compared with the spring. As a result, all the wave energy fro] is reflected back along the spring rather than being transmitted into stn the wall. Waves that travel along the spring are almost totally a ii reflected at the wall. bot If the wall is replaced with a less rigid medium, such as the heavy spring shown in Figure 29.2, some energy is transmitted into by: 442 Chapter 29 Reflection and Refraction 11110MOMMOZM daaa fieROMMUNNeaDDRadd014),, 4-403% -eardavabi swans Figure 29.1 A A wave is totally reflected when it reaches a completely rigid boundary. the new medium. Some of the wave energy is still reflected. These • •T‘ Ts aro A metal surface is rigid to light waves that shine upon it. Light energy does not propagate into the metal, but instead is returned in a reflected wave. The wave reflected from a metal surface has almost the full intensity of the incoming wave, apart from small energy losses due to the friction of the vibrating electrons in the surface. This is why metals such as silver and aluminum are so shiny. They Lir- reflect almost all the frequencies of visible light. Smooth surfaces of he these metals are therefore used as mirrors. 'S 41 Figure 29.2 When the wave reaches the =BMW heavy spring, it is partially MS, reflected. Part of the wave etiergy bounces back along the 17 111 ea0MOINDRIE 73-aaawDm 7, • fest spnrig, while the other part I.- ewes ihrij the heavy scerng he imaColawmalwODONDN 450 Other materials such as glass and water are not as rigid m wares. Like the different springs of Figure 29.2, wave energy rs both reflected and transmitted at the boundary. When light shines per- pendicularly on the surface of still water, about 2% of its energy is reflected and the rest is transmitted. When light strikes glass perpen- dicularly, about 4% of its energy is reflected. Except for slight losses, INN the rest is transmitted. 11 n. 29.2 The Law of Reflection Ilse In one dimension, reflected waves simply travel back in the direction rgy from which they came. Let a ball drop to the floor, and it bounces into straight up along its initial path. In two dimensions, the situation is a little different. Toss a ball at an angle to the floor, and it normally bounces at the same angle in a new direction. Likewise with light. The direction of incident and reflected waves is best described Lto by straight-line rays. Incident rays and reflected rays make equal angles with a line perpendicular to the surface, called the normal, as shown in Figure 29.3. The angle made by the incident ray and the normal, called the angle of incidence, is equal to the angle made by the reflected ray and the normal, called the angle of reflection. That is angle of incidence = angle of reflection Figure 29.3 It. ANGLE OF zcj I ANGLE OF In reflection, the angle between INCIDENCE ph REFLECTION the incident ray and the normal \ z ) is equal to the angle between e,(4 y, the reflected ray and the normal. MIRROR This relationship is called the law of reflection. The incident ray, the normal, and the reflected ray all lie in the same plane. The law of reflec- tion applies to both partially reflected and totally reflected waves. 29.3 Mirrors Consider a candle flame placed in front of a plane (flat) mirror. Rays of light are reflected from the nurror surface in all directions. The number of rays is infinite, and net one obeys the last at reflection. rra:mirror. Thetig%;at,s0MS4nss *oto 4 .411-fke Atts,specNNfloticelhairokliaVeladjujte orle1t4t4 Tai* *01: pareii-;tlibit-g*age is farthek awe Vagru aeifceu seClietriceS1.:,Td`d6Chitfetit- kiti , spec on the-nartb =surface rld then read the distanekeff the scale orilhecaCril'pg era's4lensit,p,,zat this process using your image in the mirror.- , When the mirror is curved, the sizes and distances of object and Figure 29.4 A image are no longer equal. The law of reflection also holds for curved A virtual image is formed behind the plane mirror and is located at mirrors.,.%every part of the surface, the angle of incidence is equal to the position where the extended the angle of reflection, as shown in Figure 29.6. Note that for a curved reflected rays (broken lines) - normals (shown as dashed black converge. mirror, unlike a plane mirror, the lines) at different points on the surface are not parallel to each other. 444 Chapter 29 Reflection and Refraction Figure 29.4 shows only two rays that originate at the tip of the candle YOU YOUR TWIN? flame and reflect from the mirror to your eye. Note that the rays Ar \iv diverge (spread apart) from the tip of the flame, and continue diverging from the mirror upon reflection. These divergent rays appear to originate from a point located behind the mirror. So You see an image of the candle in the mirror (actually behind the mir- ror). The image is called a virtual image, because light does not actually start there. Figure 29.5 A Your eye cannot ordinarily tell the difference between an object For reflection in a plane mirror, and its virtual image. This is because the light that enters your eye is object size equals image size and entering in exactly the same manner, physically, as it would without object distance equals image the mirror if there really were an object there. Notice that the image distance. is as far behind the mirror as the object is in front of the mirror. Notice also that the image and object are the same size. When you view yourself in a mirror, your image is the same size your identical twin would appear if located as far behind the minor as you are in front—as long as the minor is flat. Figure 29.6 (a) The virtual image formed by a Convex mirror la mwror that curves outward) is &nether and closer to the mirror than the object is. (b) When the object is close to a concave mirror (a mir- ror that curves inward like a "cave"), the virtual image is larger and farther away than the object is. In any case, the law of a. reflection holds for each ray. • Ouestions 1. If you look at your blue shirt in a mirror, what is the color of its image? What does this tell you about the frequency of light inci- dent upon a mirror compared with the frequency of the light after it is reflected? 2. If you wish to take a picture of your image while standing 2 m in front of a plane mirror, for what distance should you set your c, -ncra to provide sharpest focus? 11 Explore 2Develop 3 Apply • Answers 1 Laboratory Manual 75 2 Concept Development 1. The color of the image will be the same as the color of the object. This is evidence that Practice Book 29-1, 29-2 the frequency of light is not changed by reflection. 2 Laboratory Manual 76, 78 2. You should set your camera for a distance of 4 m. The situation is equivalent to your • standing 2 m in front of an open window and viewing your twin standing 2 m in back 3 Laboratory Manual 74, 77 of the window. 445 j, rj 21. , stt fl hg an Pa so to o he inittora'a, et--; th: F centimeters,sPart: twe- ein 'Etow:manytniages aret there.7 Lots! How)--itith1::;c°j11 much.nloney,.!.. , ilft` there? Unfortunatelyt' there' is still only one coin. s 29.4 Diffuse Reflection When light is incident on a rough surface. it is reflected icmain directions This is arse reflection (Figure 29.7;. bilthough the reflection of each single ray obeys the law of reflection, the many different angles that incident light rays encounter cause reflection in many directions. What constitutes a rough surface for some rays may be a pol- ished surface for others.
Load more

Recommended publications
  • The Diffuse Reflecting Power of Various Substances 1
    . THE DIFFUSE REFLECTING POWER OF VARIOUS SUBSTANCES 1 By W. W. Coblentz CONTENTS Page I. Introduction . 283 II. Summary of previous investigations 288 III. Apparatus and methods 291 1 The thermopile 292 2. The hemispherical mirror 292 3. The optical system 294 4. Regions of the spectrum examined 297 '. 5. Corrections to observations 298 IV. Reflecting power of lampblack 301 V. Reflecting power of platinum black 305 VI. Reflecting power of green leaves 308 VII. Reflecting power of pigments 311 VIII. Reflecting power of miscellaneous substances 313 IX. Selective reflection and emission of white paints 315 X. Summary 318 Note I. —Variation of the specular reflecting power of silver with angle 319 of incidence I. INTRODUCTION In all radiometric work involving the measurement of radiant energy in absolute value it is necessary to use an instrument that intercepts or absorbs all the incident radiations; or if that is impracticable, it is necessary to know the amount that is not absorbed. The instruments used for intercepting and absorbing radiant energy are usually constructed in the form of conical- shaped cavities which are blackened with lampblack, the expecta- tion being that, after successive reflections within the cavity, the amount of energy lost by passing out through the opening is reduced to a negligible value. 1 This title is used in order to distinguish the reflection of matte surfaces from the (regular) reflection of polished surfaces. The paper gives also data on the specular reflection of polished silver for different angles of incidence, but it seemed unnecessary to include it in the title.
    [Show full text]
  • Some Diffuse Reflection Problems in Radiation Aerodynamics Stephen Nathaniel Falken Iowa State University
    Iowa State University Capstones, Theses and Retrospective Theses and Dissertations Dissertations 1964 Some diffuse reflection problems in radiation aerodynamics Stephen Nathaniel Falken Iowa State University Follow this and additional works at: https://lib.dr.iastate.edu/rtd Part of the Aerospace Engineering Commons Recommended Citation Falken, Stephen Nathaniel, "Some diffuse reflection problems in radiation aerodynamics " (1964). Retrospective Theses and Dissertations. 3848. https://lib.dr.iastate.edu/rtd/3848 This Dissertation is brought to you for free and open access by the Iowa State University Capstones, Theses and Dissertations at Iowa State University Digital Repository. It has been accepted for inclusion in Retrospective Theses and Dissertations by an authorized administrator of Iowa State University Digital Repository. For more information, please contact [email protected]. This dissertation has been 65-4604 microfilmed exactly as received FALiKEN, Stephen Nathaniel, 1937- SOME DIFFUSE REFLECTION PROBLEMS IN RADIATION AERODYNAMICS. Iowa State University of Science and Technology Ph.D., 1964 Engineering, aeronautical University Microfilms, Inc., Ann Arbor, Michigan SOME DIFFUSE REFLECTIOU PROBLEMS IN RADIATION AERODYNAMICS "by Stephen Nathaniel Falken A Dissertation Submitted to the Graduate Faculty in Partial Fulfillment of The Requirements for the Degree of DOCTOR OF HîILOSOEHï Major Subjects: Aerospace Engineering Mathematics Approved: Signature was redacted for privacy. Cmrg^Vf Major Work Signature was redacted for privacy. Heads of Mgjor Departments Signature was redacted for privacy. De of Gradu^ e College Iowa State University Of Science and Technology Ames, loTfa 196k ii TABLE OF CONTENTS page DEDICATION iii I. LIST OF SYMBOLS 1 II. INTRODUCTION. 5 HI. GENERAL AERODYNAMIC FORCE ANALYSIS 11 IV. THE THEORY OF RADIATION AERODYNAMICS Ik A.
    [Show full text]
  • Ap Physics 2 Summary Chapter 21 – Reflection and Refraction
    AP PHYSICS 2 SUMMARY CHAPTER 21 – REFLECTION AND REFRACTION . Light sources and light rays Light Bulbs, candles, and the Sun are examples of extended sources that emit light. Light from such sources illuminates other objects, which reflect the light. We see an object because incident light reflects off of it and reaches our eyes. We represent the travel of light rays (drawn as lines and arrows). Each point of a shining object or a reflecting object send rays in all directions. Law of reflection When a ray strikes a smooth surface such as a mirror, the angle between the incident ray and the normal line perpendicular to the surface equals the angle between the reflected ray and the normal line (the angle of incidence equals the angle of reflection). This phenomenon is called specular reflection. Diffuse reflection If light is incident on an irregular surface, the incident light is reflected in many different directions. This phenomenon is called diffuse reflection. Refraction If the direction of travel of light changes as it moves from one medium to another, the light is said to refract (bend) as it moves between the media. Snell’s law Light going from a lower to a higher index of refraction will bend toward the normal, but going from a higher to a lower index of refraction it will bend away from the normal. Total internal reflection If light tries to move from a more optically dense medium 1 of refractive index n1 into a less optically dense medium 2 of refractive index n2 (n1>n2), the refracted light in medium 2 bends away from the normal line.
    [Show full text]
  • Method for Measuring Solar Reflectance of Retroreflective Materials Using Emitting-Receiving Optical Fiber
    Method for Measuring Solar Reflectance of Retroreflective Materials Using Emitting-Receiving Optical Fiber HiroyukiIyota*, HidekiSakai, Kazuo Emura, orio Igawa, Hideya Shimada and obuya ishimura, Osaka City University Osaka, Japan *Corresponding author email: [email protected] ABSTRACT The heat generated by reflected sunlight from buildings to surrounding structures or pedestrians can be reduced by using retroreflective materials as building exteriors. However, it is very difficult to evaluate the solar reflective performance of retroreflective materials because retroreflective lightcannotbe determined directly using the integrating sphere measurement. To solve this difficulty, we proposed a simple method for retroreflectance measurementthatcan be used practically. A prototype of a specialapparatus was manufactured; this apparatus contains an emitting-receiving optical fiber and spectrometers for both the visible and the infrared bands. The retroreflectances of several types of retroreflective materials are measured using this apparatus. The measured values correlate well with the retroreflectances obtained by an accurate (but tedious) measurement. The characteristics of several types of retroreflective sheets are investigated. Introduction Among the various reflective characteristics, retroreflective materials as shown in Fig.1(c) have been widely used in road signs or work clothes to improve nighttime visibility. Retroreflection was given by some mechanisms:prisms, glass beads, and so on. The reflective performance has been evaluated from the viewpointof these usages only. On the other hand, we have shown thatretroreflective materials reduce the heatgenerated by reflected sunlight(Sakai, in submission). The use of such materials on building exteriors may help reduce the urban heatisland effect. However, itis difficultto evaluate the solar reflective performance of retroreflective materials because retroreflectance cannot be determined using Figure 1.
    [Show full text]
  • Reflection Measurements in IR Spectroscopy Author: Richard Spragg Perkinelmer, Inc
    TECHNICAL NOTE Reflection Measurements in IR Spectroscopy Author: Richard Spragg PerkinElmer, Inc. Seer Green, UK Reflection spectra Most materials absorb infrared radiation very strongly. As a result samples have to be prepared as thin films or diluted in non- absorbing matrices in order to measure their spectra in transmission. There is no such limitation on measuring spectra by reflection, so that this is a more versatile way to obtain spectroscopic information. However reflection spectra often look quite different from transmission spectra of the same material. Here we look at the nature of reflection spectra and see when they are likely to provide useful information. This discussion considers only methods for obtaining so-called external reflection spectra not ATR techniques. The nature of reflection spectra The absorption spectrum can be calculated from the measured reflection spectrum by a mathematical operation called the Kramers-Kronig transformation. This is provided in most data manipulation packages used with FTIR spectrometers. Below is a comparison between the absorption spectrum of polymethylmethacrylate obtained by Kramers-Kronig transformation of the reflection spectrum and the transmission spectrum of a thin film. Figure 1. Reflection and transmission at a plane surface Reflection takes place at surfaces. When radiation strikes a surface it may be reflected, transmitted or absorbed. The relative amounts of reflection and transmission are determined by the refractive indices of the two media and the angle of incidence. In the common case of radiation in air striking the surface of a non-absorbing medium with refractive index n at normal incidence the reflection is given by (n-1)2/(n+1)2.
    [Show full text]
  • FTIR Reflection Techniques
    FT-IR Reflection Techniques Vladimír Setnička Overview – Main Principles of Reflection Techniques Internal Reflection External Reflection Summary Differences Between Transmission and Reflection FT-IR Techniques Transmission: • Excellent for solids, liquids and gases • The reference method for quantitative analysis • Sample preparation can be difficult Reflection: • Collect light reflected from an interface air/sample, solid/sample, liquid/sample • Analyze liquids, solids, gels or coatings • Minimal sample preparation • Convenient for qualitative analysis, frequently used for quantitative analysis FT-IR Reflection Techniques Internal Reflection Spectroscopy: Attenuated Total Reflection (ATR) External Reflection Spectroscopy: Specular Reflection (smooth surfaces) Combination of Internal and External Reflection: Diffuse Reflection (DRIFTs) (rough surfaces) FT-IR Reflection Techniques • Infrared beam reflects from a interface via total internal reflectance • Sample must be in optical contact with the crystal • Collected information is from the surface • Solids and powders, diluted in a IR transparent matrix if needed • Information provided is from the bulk matrix • Sample must be reflective or on a reflective surface • Information provided is from the thin layers Attenuated Total Reflection (ATR) - introduced in the 1960s, now widely used - light introduced into a suitable prism at an angle exceeding the critical angle for internal reflection an evanescent wave at the reflecting surface • sample in close contact Single Bounce ATR with IRE
    [Show full text]
  • Reflectance IR Spectroscopy, Khoshhesab
    11 Reflectance IR Spectroscopy Zahra Monsef Khoshhesab Payame Noor University Department of Chemistry Iran 1. Introduction Infrared spectroscopy is study of the interaction of radiation with molecular vibrations which can be used for a wide range of sample types either in bulk or in microscopic amounts over a wide range of temperatures and physical states. As was discussed in the previous chapters, an infrared spectrum is commonly obtained by passing infrared radiation through a sample and determining what fraction of the incident radiation is absorbed at a particular energy (the energy at which any peak in an absorption spectrum appears corresponds to the frequency of a vibration of a part of a sample molecule). Aside from the conventional IR spectroscopy of measuring light transmitted from the sample, the reflection IR spectroscopy was developed using combination of IR spectroscopy with reflection theories. In the reflection spectroscopy techniques, the absorption properties of a sample can be extracted from the reflected light. Reflectance techniques may be used for samples that are difficult to analyze by the conventional transmittance method. In all, reflectance techniques can be divided into two categories: internal reflection and external reflection. In internal reflection method, interaction of the electromagnetic radiation on the interface between the sample and a medium with a higher refraction index is studied, while external reflectance techniques arise from the radiation reflected from the sample surface. External reflection covers two different types of reflection: specular (regular) reflection and diffuse reflection. The former usually associated with reflection from smooth, polished surfaces like mirror, and the latter associated with the reflection from rough surfaces.
    [Show full text]
  • Emission and Reflection from the Ocean and Land Surfaces 1
    Lecture 5 Emission and reflection from the ocean and land surfaces Objectives: 1. Interaction of radiation with the surfaces. 2. Emission from the ocean and land surfaces. 3. Reflection from the ocean and land surfaces. Required reading: G: 4.3, 4.4, 4.5 Additional reading: CNES online tutorial Chapters 5-6 http://ceos.cnes.fr:8100/cdrom-00/ceos1/science/baphygb/intro/content.htm 1. Interaction of radiation and the surfaces. The ocean and land surfaces can modify the atmospheric radiation field by a) reflecting a portion of the incident radiation back into the atmosphere; b) transmitting some incident radiation; c) absorbing a portion of incident radiation (see Lecture 4, Kirchhoff’s law); d) emitting the thermal radiation (see Lecture 4, Kirchhoff’s law); INCIDENT RADIATION REFLECTED RADIATION ABSORBED RADIATION RANSMITTED RADIATION TRANSMITTED RADIATION 1 Conservation of energy requires that monochromatic radiation incident upon any surface, Ii, is either reflected, Ir, absorbed, Ia, or transmitted, It . Thus Ii = Ir + Ia + It [5.1] 1 = Ir / Ii + Ia / Ii + It / Ii = R + A+ T [5.2] where T is the transmission, A is the absorption, and R is the reflection of the surface. In general, T, A, and R are a function of the wavelength: Rλ + Aλ+ Tλ =1 [5.3] Blackbody surfaces (no reflection) and surfaces in LTE (from Kirchhoff’s law): Aλ = ελ [5.4] Opaque surfaces (no transmission): Rλ + Aλ = 1 [5.5] Thus for the opaque surfaces ελ = 1- Rλ [5.6] 2. Emission from the ocean and land surfaces. Emissivity of the surfaces: • In general, emissivity depends on the direction of emission, surface temperature, wavelength and some physical properties of the surface • In the thermal IR (4µm<λ< 100µm), nearly all surfaces are efficient emitters with the emissivity > 0.8 and their emissivity does not depend on the direction.
    [Show full text]
  • Chapter 22 Reflection and Refraction of Light Wavelength the Distance Between Any Two Crests of the Wave Is Defined As the Wavel
    Chapter 22 Reflection and Refraction of Light Wavelength Dual Nature of Light The distance between any two crests of the • Experiments can be devised that will wave is defined as the wavelength display either the wave nature or the particle nature of light • Nature prevents testing both qualities at the same time Geometric Optics – Using a Ray The Nature of Light Approximation • “Particles” of light are called photons • Light travels in a straight-line path in a • Each photon has a particular energy homogeneous medium until it –E = h ƒ encounters a boundary between two – h is Planck’s constant different media • h = 6.63 x 10-34 J s •The ray approximation is used to – Encompasses both natures of light represent beams of light • Interacts like a particle •A ray of light is an imaginary line drawn • Has a given frequency like a wave along the direction of travel of the light beams Ray Approximation Geometric Optics •A wave front is a surface passing through points of a wave that have the same phase and amplitude • The rays, corresponding to the direction of the wave motion, are perpendicular to the wave fronts Reflection QUICK QUIZ 22.1 Diffuse refection: The objects has irregularities that spread out an initially parallel beam of Which part of the figure below shows specular reflection of light in all directions to produce light from the roadway? diffuse reflection Specular reflection (mirror): When a parallel beam of light is directed at a smooth surface, it is specularly reflected in only one direction. The color of an object we see depends on two things: Law of Reflection The angle of incidence = the angle of reflection The kind of light falling on it and nature of its surface For instance, if white light is used to illuminate an object that absorbs all color other than red, the object will appear red.
    [Show full text]
  • Method of Determining the Optical Properties of Ceramics and Ceramic Pigments: Measurement of the Refractive Index
    CASTELLÓN (SPAIN) METHOD OF DETERMINING THE OPTICAL PROPERTIES OF CERAMICS AND CERAMIC PIGMENTS: MEASUREMENT OF THE REFRACTIVE INDEX A. Tolosa(1), N. Alcón(1), F. Sanmiguel(2), O. Ruiz(2). (1) AIDO, Instituto tecnológico de Óptica, Color e Imagen, Spain. (2) Torrecid, S.A., Spain. ABSTRACT The knowledge of the optical properties of materials, such as pigments or the ceramics that contain these, is a key feature in modelling the behaviour of light when it impinges upon them. This paper presents a method of obtaining the refractive index of ceramics from diffuse reflectance measurements made with a spectrophotometer equipped with an integrating sphere. The method has been demonstrated to be applicable to opaque ceramics, independently of whether the surface is polished or not, thus avoiding the need to use different methods to measure the refractive index accor- ding to the surface characteristics of the material. This method allows the Fresnel equations to be directly used to calculate the refractive index with the measured diffuse reflectance, without needing to measure just the specular reflectance. Al- ternatively, the method could also be used to measure the refractive index in transparent and translucent samples. The technique can be adapted to determine the complex refractive index of pigments. The reflectance measurement would be based on the method proposed in this paper, but for the calculation of the real part of the refractive index, related to the change in velocity that light undergoes when it reaches the material, and the imaginary part, related to light absorption by the material, the Kramers-Kronig relations would be used.
    [Show full text]
  • The Law of Reflection: the Law of Refraction
    The law of reflection: 11 The law of refraction: nn2211sin sin Snell’s Law Image formation 1 Reading: Chapter 23 2 Chapter 23 Propagation of Light - Ray Optics 3 Propagation of Light – Ray (Geometric) Optics Main assumption: light travels in a straight-line path in a uniform medium and changes its direction when it meets the surface of a different medium or if the optical properties of the medium are nonuniform The rays (directions of propagation) are straight lines perpendicular to the wave fronts The above assumption is valid only when the size of the barrier (or the size of the media) is much larger than the wavelength of light d Main Question of Ray Optics: What happens to light at the boundary between two 4 media? Propagation of Light - Ray Optics What happens to light at the boundary between two media? The light can be reflected or refracted (transmitted) 5 Reflection of Light The law of reflection: The angle of reflection is equal to the angle of incidence 11 The incident ray, the reflected ray and the normal are all in the same plane 6 Reflection of Light Specular reflection Diffuse reflection (reflection from a (reflection from a smooth surface) – rough surface) example: mirrors 7 Example: Multiple Reflection (1) The incident ray strikes the first mirror (3) (2) The reflected ray is directed (2) toward the second mirror (1) (3) There is a second reflection from the second mirror 8 Propagation of Light - Ray Optics What happens to light at the boundary between two media? The light can be reflected or refracted (transmitted)
    [Show full text]
  • 2 Reflection, Refraction, Diffraction, and Scattering
    2 Reflection, refraction, diffraction, and scattering In this chapter we will describe how radiation is reflected off a surface, transmitted into a medium at a different angle, how it is influenced by passing an edge or through an aperture, and how it is scattered and spread out by interactions with particles at various scales. We will focus on the propagation of light. In order to describe the direction in which light propagates, it is often convenient to represent a light wave by rays rather than by wave fronts. In fact, rays were used to describe the propagation of light long before its wave nature was established. Geometrically, the duality is easy to handle: Whenever we indicate the direction of propagation of light by a ray, the wave front is always locally perpendicular to the ray. 2.1 Reflection Figure 2-1. Spheres reflected in the floor and in each other. Reflection occurs when a wave hits the interface between two dissimilar media, so that all of or at least part of the wave front returns into the medium from which it originated. Common examples are reflection of light, as shown in figure 2-1, as well as reflection of surface waves that may be observed in a pool of water, or sound waves reflected as echo from a wall. Reflection of light may be specular or diffuse. The first occurs on a blank mirroring surface that retains the geometry of the beams of light. The second occurs on a rougher surface, not retaining the imaging geometry, only the energy. © Fritz Albregtsen 2008 2-2 Reflection, refraction, diffraction, and scattering 2.1.1 Reflectance Reflectance is the ratio of reflected power to incident power, generally expressed in decibels or percent.
    [Show full text]