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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 distinguish between the absorption, reflection, refraction and scattering of light and identify everyday situations where each occurs 5.6.4a 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 principles, concepts and ideas in physics P2. applies the processes that are used to test and validate models, theories and laws of science with particular emphasis on first-hand investigations in physics P3. assesses the impact of particular technological advances on understanding in physics P4. describes applications of physics which affect society or the environment Major concepts Energy transformations Energy transfer – including reflection, refraction Models: transverse and longitudinal wave models, mathematical models (equations e.g. v = f) Theories: electromagnetic wave theory Laws: Inverse square law, Snell’s law, law of reflection Production, modulation and reception of radio waves Production of microwaves, digital encoding of information Mobile phone, fax/modem, radio, television 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 1. The World Communicates The wave model can be used to explain how current technologies transfer information describe waves as a transfer of energy disturbance that may occur in one, two or three dimensions, depending on the nature of the wave and the medium perform a first-hand investigation to observe and gather information about the transmission of waves in: – slinky springs – water surfaces – ropes or use appropriate computer simulations 1. Identify two types of waves that can be produced in a spring and use diagrams to clarify the difference between these waves. (4M) 2. Compare surface water waves with a transverse wave travelling through a spring. (2M) 3. Discuss the usefulness of computer simulations. (5M) describe the relationship between particle motion and the direction of energy propagation in transverse and longitudinal waves present diagrammatic information about 4. Describe the relative motion of the transverse and longitudinal waves, particles and the direction of energy direction of particle movement and the propagation in a transverse wave. direction of propagation 5. Describe the relative motion of the particles and the direction of energy propagation in a longitudinal wave. present and analyse information from displacement-time graphs for transverse wave motion 6. The adjacent diagram (a) shows a displacement-time graph for a transverse wave pulse travelling along a spring. Interpret this graph. (2M) 7. A long spring was made to vibrate define and apply the following terms to the wave model: medium, displacement, amplitude, period, compression, rarefaction, crest, trough, transverse waves, longitudinal waves, frequency, wavelength, velocity 8. Contrast transverse and longitudinal waves. (2M) 9. With the aid of a diagram, define the terms amplitude, wavelength, crest and trough of a transverse wave. (4M) 10. With the aid of a 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 require a medium for propagation while electromagnetic waves do not 13. Contrast the propagation of a mechanical wave and an electromagnetic wave. 14. List the components of the electromagnetic spectrum in order of increasing wavelength describe electromagnetic waves in terms of their speed in space and their lack of requirement of a medium for propagation [from section 8.2.3] 15. Compare the speed of light and X-rays in a vacuum. (1M) perform a first-hand investigation to gather information about the frequency and amplitude of waves using an oscilloscope or electronic data-logging equipment 16. Recount how you varied the frequency of a wave and sketch the effect seen on the CRO/data logging equipment of changing only the frequency. 17. Sketch two waves having the same 2 8.2 The World Communicates frequency but different amplitudes. 18. Describe the key features of a data logger. plan, choose equipment for and perform 19. Propose a procedure that could be a first-hand investigation to gather followed to investigate the relationship information to identify the relationship between the frequency and between the frequency and wavelength wavelength of a sound wave. In your of a sound wave travelling at a constant answer, identify the independent and velocity dependent variables. (6M) 20. Describe how data obtained in a firsthand 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 between velocity, frequency and wavelength for a wave: solve problems and analyse information 21. The speed of sound in air is 340 m s-1. by applying the mathematical model of Calculate the wavelength of the musical note, used as a reference tone v f by musicians, having a frequency of to a range of situations 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 transformations required in one of the following: – mobile telephone – fax/modem – radio and television v f 25. Identify the energy transformation that takes place in the speaker of a mobile phone. (1M) 26. Identify the energy 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 3 8.2 The World Communicates 31. Describe a sound wave. (2M) 32. Contrast a sound wave with an electromagnetic wave. (4M) identify that sound waves are vibrations or oscillations of particles in a medium explain qualitatively that pitch is related to frequency and volume to amplitude of sound waves perform a first-hand investigation and 33. Identify the physical property of a gather information to analyse sound sound wave that is responsible for the waves from a variety of sources using human perception of pitch. (1M) the Cathode Ray Oscilloscope (CRO) or 34. What is the term used to classify an alternate computer technology sounds having a pitch 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) 37. The graphs in figure (a) represent fig (a) 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 of a sound wave 38. Account for the 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 rarefactions of sound waves to the crests and troughs of transverse waves used to represent them 40. Using a quantitative time axis, graph qualitatively the pressure changes at a fixed point in a medium through 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 superposition and compare the resulting waves to the original waves in sound perform a first-hand investigation, 43. Describe in words the principle of gather, process and present information superposition as it applies to sound using a CRO or computer to waves. demonstrate the principle of 44. Outline a first-hand investigation superposition for two waves travelling in carried out to demonstrate the the same medium superposition of waves. (3M) present graphical information, solve problems and analyse information involving superposition of sound waves 45. Draw a graph showing the waveform that is produced by the superposition of the two waves in the adjacent graph. xxxx 3. Recent technological developments have allowed greater 4 8.2 The World Communicates use of the electromagnetic spectrum identify the electromagnetic wavebands filtered out by the atmosphere, especially UV, X-rays and gamma rays 46. Identify three types of electromagnetic waves that are strongly absorbed by the 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 detection of various wavebands in the electromagnetic spectrum 48. Identify three methods of detecting visible light. (3M) 49. Tabulate a method for detecting each waveband in the electromagnetic spectrum. (10M) explain that the relationship between the intensity of electromagnetic radiation and distance from a source is an example of the inverse square law: plan, choose equipment or resources for and perform a first-hand investigation and gather information to model the inverse square law for light intensity and distance from the source 50. State the inverse square law for light verbally. (2M) 51. Represent the inverse square law for light using symbols. 52. The light intensity 2 m from a point source is 18 milliwatts per square 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] I 1 d2 analyse information to identify the 54. Identify the type of wave that carries waves involved in the transfer of energy information between a mobile phone that occurs during the use of one of the and the base station. (2M) following: 55. Identify the type of wave most closely – mobile phone associated with the operation of the microphone and speaker in a mobile – television phone. (1M) – radar 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 the 58. Identify four communication electromagnetic spectrum range utilised technologies, each of which makes in modern communication technologies use of a different part of the electromagnetic spectrum and identify the type of wave used. (4M) outline how the modulation of amplitude or frequency of visible light, microwaves and/or radio waves can be used to transmit information 59. Use a diagram to clarify how a sound wave can be encoded using amplitude modulation. (3M) 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 the limited range of the electromagnetic spectrum available for communication purposes 62. 5 8.2 4. The World Communicates Many communication technologies use applications of reflection and refraction of electromagnetic waves describe and apply the law of reflection and explain the effect of reflection from a plane surface on waves perform first-hand investigations and gather information to observe the path of light rays and construct diagrams indicating both the direction of travel of the light rays and a wave front 63. State the law of reflection. (2M) 64. Draw a diagram to show the path of a ray of light striking a plane mirror with an angle of incidence of 20°. describe one application of reflection for each of the following: – plane surfaces – concave surfaces – convex surfaces – radio waves being reflected by the ionosphere present information using ray diagrams to show the path of waves reflected from: – plane surfaces – concave surfaces – convex surface – the ionosphere 65. Identify one application of reflection waves from a plane surface. (1M) 66. Describe one application of reflection of waves from a concave surface. (2M) 67. Identify the type of 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 applications of reflection of light, radio waves and microwaves have assisted in information transfer 71. Describe how applications of physics have affected society. In your answer, refer specifically to light, microwaves and radio waves. (6M) [P4] explain that refraction is related to the velocities of a wave in different media and outline how this may result in the bending of a wave front perform an investigation and gather information to graph the angle of incidence and refraction for light encountering a medium change showing the relationship between these angles 72. Account for the refraction of light passing from one medium to another. (2M). 73. Describe two situations in which light passing from one medium to another would not 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 investigation and gather information to calculate the refractive index of glass or Perspex 75. Recount the procedure that you used to gather first-hand information to enable you to calculate the refractive 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 6 8.2 The World Communicates index? (2M) define refractive index in terms of changes in the velocity of a wave in passing from one medium to another define Snell’s Law: solve problems and analyse information 81. Calculate the angle of refraction when using Snell’s Law a ray of light travelling in air enters a 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 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] v1 sin i v2 sin r 78. Define refractive index of a medium in terms of the velocity of light in a vacuum 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) identify the conditions necessary for total internal reflection with reference to the critical angle [Important for HSC course – Medical Physics] 87. Use a labelled diagram to describe the process of total internal reflection in an optical fibre. (5M) 88. Identify the conditions necessary for total internal reflection to occur. (3M) outline how total internal reflection is used in optical fibres [Important for HSC course – Medical Physics] 89. Outline two applications of optical fibres. (2M) 90. Describe how the application of total internal reflection has affected society. (5M) [P4] 91. Contrast the storage of information in analogue and digital forms. (2M) 5. Electromagnetic waves have potential for future communication technologies and data storage technologies identify types of communication data that are stored or transmitted 7 8.2 The World Communicates 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, process 94. Discuss some of the physical and present information from secondary principles applied in the operation sources to identify areas of current of the GPS. (6M) [P5] research and use the available 95. Describe the effects on society of evidence to discuss some of the the application of physics to the underlying physical principles used in GPS. (5M) [P4] one 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] 8