8 2 the World Communicates

8.2 The World Communicates

Assumed Knowledge Domain: knowledge and understanding: c Refer to the Science Stages 4–5 Syllabus for the following: 5.6.1a identify waves as carriers of energy 5.6.1b qualitatively describe features of waves including frequency, wavelength and speed 5.6.1c give examples of different types of radiation that make up the electromagnetic spectrum and identify some of their uses 5.6.4a distinguish between the absorption, reflection, refraction and scattering of light and identify everyday situations where each occurs 5.9.1b identify that some types of electromagnetic radiation are used to provide information about the universe 5.12c describe some everyday uses and effects of electromagnetic radiation, including applications in communication technology.

Physics PFAs (from table 7.1) in this module of work P1. outlines the historical development of major Major concepts principles, concepts and ideas in physics . Energy transformations . Energy transfer – including reflection, refraction P2. applies the processes that are used to test and Models: transverse and longitudinal wave models, validate models, theories and laws of science mathematical models (equations e.g. v = with particular emphasis on first-hand f) investigations in physics Theories: electromagnetic wave theory Laws: Inverse square law, Snell’s law, law of reflection P3. assesses the impact of particular technological . Production, modulation and reception of radio advances on understanding in physics waves . Production of microwaves, digital encoding of information P4. describes applications of physics which affect . Mobile phone, fax/modem, radio, television society or the environment . Amplitude and frequency modulation, digital encoding . Optical fibre use – communication, medical (endoscopes) P5. describes the scientific principles employed in particular areas of research in physics

1 8.2 The World Communicates

1. The wave model can be used to explain how current technologies transfer information . describe waves as a transfer of . perform a first-hand 1. Identify two types of waves energy disturbance that may investigation to observe and that can be produced in a occur in one, two or three gather information about the spring and use diagrams to dimensions, depending on the transmission of waves in: clarify the difference between nature of the wave and the – slinky springs these waves. (4M) medium – water surfaces 2. Compare surface water waves – ropes with a transverse wave travelling through a spring. or use appropriate computer (2M) simulations 3. Discuss the usefulness of computer simulations. (5M) . describe the relationship . present diagrammatic 4. Describe the relative motion of between particle motion and information about transverse the particles and the direction the direction of energy and longitudinal waves, of energy propagation in a propagation in transverse and direction of particle movement transverse wave. longitudinal waves and the direction of 5. Describe the relative motion of propagation the particles and the direction of energy propagation in a longitudinal wave. . . present and analyse 6. The adjacent diagram (a) information from displacement- shows a displacement-time time graphs for transverse graph for a transverse wave wave motion pulse travelling along a spring. Interpret this graph. (2M) 7. A long spring was made to vibrate . define and apply the following . 8. Contrast transverse and terms to the wave model: longitudinal waves. (2M) medium, displacement, 9. With the aid of a diagram, amplitude, period, compression, define the terms amplitude, rarefaction, crest, trough, wavelength, crest and trough transverse waves, longitudinal of a transverse wave. (4M) waves, frequency, wavelength, 10. With the aid of a velocity diagram, define the terms amplitude, wavelength, compression and rarefaction of a longitudinal wave. (4M) 11. Define the terms frequency and period of a wave and state how they are related to each other. (3M) 12. Tabulate the following quantities, showing the symbol for each quantity the symbol for the quantity, the unit used to measure that quantity and the symbol for the unit: velocity, frequency, wavelength, period, amplitude. (5M) . identify that mechanical waves . 13. Contrast the propagation require a medium for of a mechanical wave and an propagation while electromagnetic wave.

electromagnetic waves do not 14. List the components of the electromagnetic spectrum in order of increasing wavelength . describe electromagnetic waves . 15. Compare the speed of in terms of their speed in space light and X-rays in a vacuum. and their lack of requirement of (1M) a medium for propagation [from section 8.2.3] . . perform a first-hand 16. Recount how you varied investigation to gather the frequency of a wave and information about the sketch the effect seen on the frequency and amplitude of CRO/data logging equipment waves using an oscilloscope or of changing only the electronic data-logging frequency. equipment 17. Sketch two waves having the same frequency but different amplitudes. 18. Describe the key features of a data logger. . . plan, choose equipment for and 19. Propose a procedure that perform a first-hand could be followed to investigation to gather investigate the relationship information to identify the between the frequency and relationship between the wavelength of a sound wave. frequency and wavelength of a In your answer, identify the sound wave travelling at a independent and dependent constant velocity variables. (6M) 20. Describe how data obtained in a first-hand investigation was analysed to identify the relationship between frequency and wavelength of a sound wave, and state the conclusion the analysis produced. (4M) . quantify the relationship . solve problems and analyse 21. The speed of sound in air between velocity, frequency information by applying the is 340 m s-1. Calculate the and wavelength for a wave: mathematical model of wavelength of the musical v = fl v = fl note, used as a reference tone to a range of situations by musicians, having a frequency of 440 Hz? 22. The velocity of electromagnetic radiation is XXXXXX m s-1. Calculate the wavelength of the radio waves produced by NOVA 96.9, having a frequency of 96.9 MHz. 23. Compare the wavelength of the radio waves used by NOVA FM with the wavelength of the microwaves produced in a microwave oven, given that these waves have a frequency of XXXX gigahertz. 24. Astronomers gather information about hydrogen in the universe using

electromagnetic radiation that gas emits, which has a wavelength of XXXX 8 cm. Calculate the frequency of this radiation. . describe the energy . 25. Identify the energy transformations required in one transformation that takes of the following: place in the speaker of a – mobile telephone mobile phone. (1M) – fax/modem 26. Identify the energy – radio and television transformation that takes place in the antenna of a mobile phone when it receives a signal. (1M) 27. Identify the energy transformation that takes place in the battery of a mobile phone. (1M) 28. Identify the component of a mobile phone that converts sound energy into electrical energy. (1M) 29. Identify the part of a mobile phone that converts electrical energy to electromagnetic energy in the form of microwaves. (1M) 30. Outline the usefulness of converting electrical energy to light energy in a mobile phone. (2M) 2. Features of a wave model can be used to account for the properties of sound . identify that sound waves are . 31. Describe a sound wave. vibrations or oscillations of (2M) particles in a medium 32. Contrast a sound wave with an electromagnetic wave. (4M) . explain qualitatively that pitch . perform a first-hand 33. Identify the physical is related to frequency and investigation and gather property of a sound wave that volume to amplitude of sound information to analyse sound is responsible for the human waves waves from a variety of sources perception of pitch. (1M) using the Cathode Ray 34. What is the term used to Oscilloscope (CRO) or an classify sounds having a pitch alternate computer technology higher than can be heard by the human ear? (1M) 35. Identify the property of a sound wave that is responsible for its volume (loudness). (1M) 36. Propose two changes that could be made independently of each other, each of which could make an audible sound inaudible. (2M) fig (a) 37. The graphs in figure (a) represent CRO traces of two sounds. Describe the audible

differences that a human observer would hear between these two sounds. (2M) . explain an echo as a reflection . 38. Account for the of a sound wave production of an echo. (2M) 39. Explain how an echo can be used to determine the distance from an observer to an object and state one example of the use of this from the natural world and an application of this in medicine. (5M) . relate compressions and . 40. Using a quantitative time rarefactions of sound waves to axis, graph qualitatively the the crests and troughs of pressure changes at a fixed transverse waves used to point in a medium through represent them which a 100 Hz sound wave is travelling. (2M) 41. A sound wave is sometimes represented as a transverse wave. Outline the significance of the “crests and troughs” on such a graph. (2M) 42. The adjacent diagram represents a sound wave traveling at 340 m s-1. (a) Draw a corresponding transverse wave to represent this wave at this point in time. (2M). (b) Draw a graph of the pressure change at point “X”, showing the next ___ seconds. . describe the principle of . perform a first-hand 43. Describe in words the superposition and compare the investigation, gather, process principle of superposition as it resulting waves to the original and present information using a applies to sound waves. waves in sound CRO or computer to 44. Outline a first-hand demonstrate the principle of investigation carried out to superposition for two waves demonstrate the superposition travelling in the same medium of waves. (3M) . . present graphical information, 45. Draw a graph showing solve problems and analyse the waveform that is produced information involving by the superposition of the two superposition of sound waves waves in the adjacent graph. xxxx 3. Recent technological developments have allowed greater use of the electromagnetic spectrum . identify the electromagnetic . 46. Identify three types of wavebands filtered out by the electromagnetic waves that atmosphere, especially UV, X- are strongly absorbed by the rays and gamma rays Earth’s atmosphere. 47. Account for the need to conduct investigations of objects in the universe that produce X-rays using detecting

on board satellites in orbit around the Earth. . identify methods for the . 48. Identify three methods of detection of various wavebands detecting visible light. (3M) in the electromagnetic 49. Tabulate a method for spectrum detecting each waveband in the electromagnetic spectrum. (10M) . explain that the relationship . plan, choose equipment or 50. State the inverse square between the intensity of resources for and perform a law for light verbally. (2M) electromagnetic radiation and first-hand investigation and 51. Represent the inverse distance from a source is an gather information to model the square law for light using example of the inverse square inverse square law for light symbols. law: intensity and distance from the 52. The light intensity 2 m 1 source from a point source is 18 I ө 2 milliwatts per square d centimetre. Calculate the light intensity from the same source at a distance of 6 m. 53. Outline how the inverse square law has been validated. (3M) [P2] . . analyse information to identify 54. Identify the type of wave the waves involved in the that carries information transfer of energy that occurs between a mobile phone and during the use of one of the the base station. (2M) following: 55. Identify the type of wave – mobile phone most closely associated with – television the operation of the – radar microphone and speaker in a mobile phone. (1M) 56. Identify the type of wave that allows images to be viewed using a mobile phone. (1M) 57. Compare the transmission of a standard text message using a mobile phone with the transfer of an mp3 file from one phone to another using Bluetooth. (4M) . . analyse information to identify 58. Identify four the electromagnetic spectrum communication technologies, range utilised in modern each of which makes use of a communication technologies different part of the electromagnetic spectrum and identify the type of wave used. (4M) . outline how the modulation of . 59. Use a diagram to clarify amplitude or frequency of how a sound wave can be visible light, microwaves and/or encoded using amplitude radio waves can be used to modulation. (3M) transmit information 60. Outline the application of the principle of superposition to the transmission of information using AM radio. (3M) 61. Identify the type of

modulation represented by the diagram (left). (1M) . discuss problems produced by . 62. the limited range of the electromagnetic spectrum available for communication purposes 4. Many communication . . technologies use applications of reflection and refraction of electromagnetic waves . describe and apply the law of . perform first-hand 63. State the law of reflection and explain the effect investigations and gather reflection. (2M) of reflection from a plane information to observe the path 64. Draw a diagram to show surface on waves of light rays and construct the path of a ray of light diagrams indicating both the striking a plane mirror with an direction of travel of the light angle of incidence of 20°. rays and a wave front . describe one application of . present information using ray 65. Identify one application reflection for each of the diagrams to show the path of of reflection waves from a following: waves reflected from: plane surface. (1M) – plane surfaces – plane surfaces 66. Describe one application – concave surfaces – concave surfaces of reflection of waves from a – convex surfaces – convex surface concave surface. (2M) – radio waves being reflected – the ionosphere 67. Identify the type of by the ionosphere reflector that would be useful at a “blind” intersection on a road and outline the benefits that this type of reflector produces. (3M) 68. FM radio stations in Sydney and Melbourne may have the same frequency, whereas AM station frequencies are allocated in these cities so that they are not the same. Account for this with reference to the ionosphere. (3M) 69. Compare the reflection of parallel rays from a concave and a convex mirror using ray diagrams. (4M) 70. Describe how applications of reflection of light have affected society. (4M) [P4] . describe ways in which . 71. Describe how applications of reflection of applications of physics light, radio waves and have affected society. In microwaves have assisted in your answer, refer information transfer specifically to light, microwaves and radio waves. (6M) [P4] . explain that refraction is related . perform an investigation and 72. Account for the refraction to the velocities of a wave in gather information to graph the of light passing from one different media and outline how angle of incidence and medium to another. (2M).

this may result in the bending refraction for light encountering 73. Describe two situations in of a wave front a medium change showing the which light passing from one relationship between these medium to another would not angles be refracted. (2M) 74. Identify the key difference that you would observe between two graphs, one plotting angle of incidence (i) against angle of refraction (r) and the other plotting sin(i) against sin(r) for light passing from one medium to another. (1M) . . perform a first-hand 75. Recount the procedure investigation and gather that you used to gather first- information to calculate the hand information to enable refractive index of glass or you to calculate the refractive Perspex index of a transparent medium. In your answer, identify the independent and dependent variables as well as variables that were kept constant. (6M) 76. Describe how you ensured that data collected was valid. (2M) 77. How did you check the reliability of the result you obtained for the refractive index? (2M) . define refractive index in terms . 78. Define refractive index of of changes in the velocity of a a medium in terms of the wave in passing from one velocity of light in a vacuum medium to another and in the medium and write this definition using appropriate symbols. (2M) 79. Calculate the refractive index of glass in which the speed of light is 2 x 108 m s-1. (2M) 80. The refractive index of water is 1.5. Calculate the speed of light in water. (2M) . define Snell’s Law: . solve problems and analyse 81. Calculate the angle of information using Snell’s Law refraction when a ray of light v1 sini = travelling in air enters a v2 sinr medium in which its velocity is 2 x 108 m s-1 at an angle of incidence of 30°. (2M) 82. The path of a ray of light travelling in a vacuum is changed by 5° when it enters a medium at an angle of 40° to the normal. Draw a diagram to represent this and calculate the velocity of light in the medium. (3M) 83. Light passed from a medium having a refractive

8.2 The World Communicates

index of 1.7 into one having a refractive index of 1.3. Calculate the angle of incidence if the angle of refraction was 89°. 84. When white light is passed through a prism as shown in the adjacent diagram, it is dispersed and a spectrum is produced. State two deductions, related to Snell’s law, evident from this diagram. 85. The refractive index of liquid mercury is 1.62. A ray of light travelling through mercury (a very bright light!) strikes the mercury-air interface at an angle of 30° as shown in the diagram. Calculate the angle of refraction. 86. Outline how Snell’s law has been validated. (3M). [P2] . identify the conditions . 87. Use a labelled diagram to necessary for total internal describe the process of total reflection with reference to the internal reflection in an optical critical angle fibre. (5M) [Important for HSC course – 88. Identify the conditions Medical Physics] necessary for total internal reflection to occur. (3M) . outline how total internal . 89. Outline two applications reflection is used in optical of optical fibres. (2M) fibres 90. Describe how the [Important for HSC course – application of total internal Medical Physics] reflection has affected society. (5M) [P4] 5. Electromagnetic waves have potential for future communication technologies and data storage technologies . identify types of communication . 91. Contrast the storage of data that are stored or information in analogue and transmitted digital forms. (2M) in digital form 92. Identify types of data that are stored or transmitted in digital form. (3M) 93. Contrast the transmission of information by an FM radio station with the transmission of information by a mobile phone. (6M) . . identify data sources, gather, 94. Discuss some of the process and present physical principles applied information from secondary in the operation of the sources to identify areas of GPS. (6M) [P5]

current research and use the 95. Describe the effects available evidence to discuss on society of the some of the underlying physical application of physics to principles used in one the GPS. (5M) [P4] application of physics related to waves, such as: – Global Positioning System – CD technology – the internet (digital process) – DVD technology . . 96. Identify three laws encountered in this unit of work and describe how laws are validated in physics. (5M) [P2]