CHAPTER 10. Knowledge

Size: px

Start display at page:

Download "CHAPTER 10. Knowledge"

Gordon Riley
5 years ago
Views:

1 CHAPTER 10 Review K/U Knowledge/Understanding T/I Thinking/Investigation C Communication A Application Knowledge For each question, select the best answer from the four alternatives. 1. A light wave travels in a medium with a low index of refraction. A portion of this light is reflected off a medium with a higher index of refraction. The reflected light will experience a phase change of (a) 08 (b) 458 (c) 908 (d) 1808 (10.1) K/U 2. Monochromatic light of wavelength l strikes perpendicular to the surface of a soap bubble with uniform thickness. The light interferes constructively. Possible values for the thickness of the bubble are (a) 1l, 5l, 7l (b) 1 2 l, 3 2 l, 5 2 l (c) 2l, 4l, 6l (d) 1 4 l, 3 4 l, 5 l (10.1) T/I 4 3. The wavelength of light in a certain thin film is 70 % of its wavelength in a vacuum. What is the index of refraction of the thin film? (10.1) K/U (a) 0.75 (b) 1.00 (c) 1.33 (d) Figure 1 shows a light ray incident on a thin film of oil with an index of refraction of 1.41 spread across a block of glass with an index of refraction of Which statement is true? (10.1) K/U (a) Only ray 2 undergoes a phase change. (b) Only ray 3 undergoes a phase change. (c) Rays 2 and 3 both undergo a phase change. (d) Rays 1, 2, and 3 undergo a phase change. air n air 1.00 oil film n film 1.41 glass n glass 1.52 Figure 1 incident light ray 2 ray 1 ray 3 (transmitted ray) t 5. The incident light in Figure 1 has wavelength l in air. The minimum thickness for the film to cause constructive interference is (a) 1 l 2 n film (b) 1 l 4 n film (c) ln film (d) 2ln film (10.1) T/I 6. Monochromatic light of wavelength l passes through a slit and creates a central maximum with diameter d on a screen, located a distance L away. What is the diameter of the slit? (10.2) T/I (a) 2lL d (b) 2l Ld (c) Ld l (d) 1 2 a L ld b 7. Optical resolution will increase by (a) increasing the frequency of light (b) decreasing the aperture size (c) decreasing the intensity of light (d) increasing the aperture size (10.2) K/U 8. Monochromatic light passes through a grating with slit spacing w. The fifth maximum falls at an angle u. What is the wavelength of the light? (10.3) K/U T/I (a) 1 5 w sin u (b) 5 sin u w (c) 5 2 w sin u (d) 1 sin u 5 w 9. A transmission grating has lines/cm. Determine the distance between adjacent slits. (10.3) T/I (a) m (b) m (c) m (d) m 550 Chapter 10 Applications of the Wave Nature of Light NEL

2 10. Electromagnetic waves consist of magnetic and electric fields that are (a) parallel to each other and to the direction of propagation, and oscillate in phase (b) perpendicular to each other and to the direction of propagation, and oscillate in phase (c) parallel to each other and to the direction of propagation, and oscillate out of phase (d) perpendicular to each other and to the direction of propagation, and oscillate out of phase (10.4) K/U 11. A microwave oven operates at a frequency of 2.45 GHz. What is the wavelength of the microwaves? (10.4) T/I (a) mm (b) cm (c) m (d) m 12. Malus s law relates (a) the refracted intensity to the transmitted intensity (b) the incident intensity to the refracted intensity (c) the transmitted intensity to the incident intensity (d) the incident intensity to the reflected intensity (10.5) K/U 13. Engineers often analyze the design of a large structure by constructing Lucite models. This process enables engineers to measure which property of the real structure? (10.6) K/U (a) the effect on atmospheric pressure waves (b) the interference with radio and cellphone signals (c) the reflection of light from the material s surface (d) the stresses within the structure 14. Dennis Gabor demonstrated holography by using (a) ultraviolet light (b) visible light (c) a laser (d) infrared light (10.7) K/U 15. Researchers have found that GPS systems may have direct harmful effects on which of the following? (10.8) K/U (a) brain (b) eyes (c) heart (d) ears Indicate whether each statement is true or false. If you think the statement is false, rewrite it to make it true. 16. Newton s rings can be used to detect very small flaws in the shape of a convex lens. (10.1) K/U 17. When light travelling inside water reflects from a piece of crown glass, the reflected light wave will experience a 1808 phase change. (10.1) K/U 18. A phase change of 1808 corresponds to waves that are separated by one-half of a wavelength. (10.1) K/U 19. The particle theory of light best explains the bright and dark fringes surrounding the central maximum in a single-slit diffraction demonstration. (10.2) K/U 20. To achieve the best possible resolution of their images, astronomers try to maximize the effects of diffraction from distant stars. (10.2) K/U 21. Doubling the wavelength of light in a single-slit diffraction pattern will increase the diameter of the central maximum by four times. (10.2) K/U 22. Diffraction of sunlight through a single slit may not be noticed because sunlight has all the visible wavelengths, and the fringes of each wavelength overlap. (10.2) K/U 23. A CD is a good example of a transmission grating. (10.3) K/U 24. Increasing the number of lines per centimetre in a transmission grating will also increase the diffraction angle. (10.3) K/U 25. Diffraction gratings will display interference patterns only for visible light wavelengths if the slit spacing is appropriate. (10.3) K/U 26. Gamma rays travel through a vacuum at a higher speed than microwaves. (10.4) K/U 27. Microwave ovens work by radiating the food with waves of select frequencies that interact strongly with water and carbon dioxide molecules. (10.4) K/U 28. Light from the Sun is linearly polarized before reflecting off particles in the atmosphere. (10.5) K/U 29. When light reflects off a transparent surface at Brewster s angle, the reflected light is entirely polarized. (10.5) K/U 30. Lidar technology relies on visible light. (10.6) K/U 31. Photoelasticity is a property of certain materials that allows engineers to measure the stress distribution in a structure. (10.6) K/U 32. The technique of holography allows us to store, retrieve, and process information optically. (10.7) K/U 33. All technology is beneficial and has no shortcomings. (10.8) K/U Understanding 34. Many camera lenses are manufactured with a thin film over the glass to minimize reflection. Using diagrams and words, explain how this anti-reflective coating works. Discuss how the following variations will affect the properties of the anti-reflective coating. (10.1) K/U C A (a) changing the wavelength of light (b) changing the angle of incidence of light NEL Chapter 10 Review 551

3 35. A light ray passes through the normal to the surface of a thin film of thickness t. One portion of the light ray reflects off the top of the film. Another portion transmits through the film, reflects off the bottom of the film, and returns to the top of the film. What is the path difference between these two reflected rays? (10.1) K/U 36. (a) Explain what is meant by a thin film. (b) Approximately how thin must a transparent film be to achieve optical interference? (10.1) K/U C 37. Explain why it is impossible to see interference effects in thick films. (10.1) K/U 38. Describe two factors that affect the angle of diffraction as monochromatic light passes through a small opening. (10.2) K/U 39. Do the maxima created by a diffraction grating all have the same intensity? (10.3) K/U 40. Sometimes, your car radio loses reception as you drive around mountains or over long distances where the curvature of Earth becomes a factor. Generally, FM waves are lost more readily than AM waves. Given that FM waves are measured in megahertz, and AM waves are measured in kilohertz, explain why the FM waves lose reception before the AM waves. (10.4) K/U T/I A 41. Your friend insists that he is listening to a radio wave. State the differences between a sound wave and a radio wave, and explain how information from the radio station reaches the listener s ear. (10.4) K/U C 42. When a radio transmitter uses a vertical antenna, the best reception occurs when the receiver also uses a vertical antenna. Explain why a horizontal antenna would give poorer reception. (10.4) K/U A 43. Explain the term optically active, and describe two devices around your home that make use of optical activity. (10.5) K/U C A 44. Describe how you can tell whether or not a pair of sunglasses is polarized. (10.5) K/U C Analysis and Application 45. A thin film of soapy water with an index of refraction of 1.35 has a thickness of m at one point. This film is surrounded by air. (10.1) T/I (a) Determine the three longest wavelengths of light that will interfere constructively when reflecting from the soapy film. (b) Which of these wavelengths is visible? 46. A plastic film with a thickness of 250 nm appears to be green when light with a wavelength of nm illuminates it. Calculate the index of refraction when viewed in reflection at normal incidence (Figure 2). (10.1) T/I air plastic t air Figure A thin film with an index of refraction of 1.45 is spread across flint glass with an index of refraction of Green light with a wavelength of 560 nm, from the air, hits the thin film nearly perpendicular to the surface. (10.1) T/I (a) Calculate the wavelength of green light in the film. (b) Determine whether the waves experience a phase change when reflecting from the air film surface and from the film glass surface. (c) Calculate the minimum thickness of the film that will create constructive interference of the green light. 48. A group of students uses thin-film interference in an air wedge to calculate the thickness of a human hair. The hair is sandwiched at the ends of two microscope slides each of length 6.0 cm. The students count 25 evenly spaced interference fringes when red light with a wavelength of m illuminates the slides. Calculate the thickness of the hair. (10.1) T/I 49. A thin-film coating with a refractive index of 1.39 is used on a camera lens that has a refractive index of 1.47 to cancel out reflected light with a wavelength of m. (10.1) T/I (a) Calculate the minimum thickness for the coating that will accomplish this anti-reflection. (b) The manufacturers report that they cannot apply a coating this thin. Determine the next two possible thicknesses that will also accomplish this anti-reflection. 50. A CD uses the interference of reflected waves from the CD to encode information. Light from a red laser with a wavelength of 630 nm is reflected from small pits in the CD, and waves from the bottom of a pit and the adjacent top edge interfere. Determine the minimum pit depth that would cause the two light waves to interfere destructively. Assume that the pit is on the surface of the CD so that the region above the pit is air. (10.1) T/I A 552 Chapter 10 Applications of the Wave Nature of Light NEL

4 51. The pits on a CD are covered with a layer of plastic so that surface scratches do not damage the pits. The index of refraction of the plastic coating is n Calculate the minimum pit depth needed to produce destructive interference using reflected light with l nm (Figure 3). (10.1) T/I A Figure 3 t? 52. Two glass plates are arranged so that light reflected from the bottom surface of the top plate interferes with light reflected from the top surface of the bottom plate. Moving along the x-axis, the total reflected intensity alternates between bright and dark fringes. There are 25 bright fringes across the entire width of the plates. Determine the plate spacing at the right edge. Assume that the source of illumination is blue light with a wavelength of 420 nm. (10.1) T/I 53. A device called a Fabry Perot interferometer contains two parallel mirrors as shown in Figure 4. Multiple reflections occur between the inner mirror surfaces, and the waves transmitted at the top can interfere. Assume that the light waves travel nearly perpendicular to the mirrors, the transmitted waves interfere constructively, and the spacing between the mirrors is exactly 3.5 mm. What is a possible value for the wavelength in the visible range between 600 nm and 700 nm? (10.1) T/I Figure 4 These waves interfere. mirrors 54. Light rays with a wavelength of 350 nm perpendicularly strike two flat glass surfaces separated by an air layer. Use a diagram to support your reasoning in both of the following questions. (10.1) T/I C (a) Calculate the thickness of the air layer needed to make the glass appear bright when the light is reflected. (b) Calculate the thickness of the air layer needed to make the glass appear opaque when the light is reflected. 55. Two glass plates are separated on one side by a strip of paper cm thick. The plates are 9.8 cm long and are touching at the other end. The distance between the second and eighth dark bands is 1.23 cm. Calculate the wavelength of the light. (10.1) T/I 56. A beam of green light with a wavelength of 560 nm passes through a single slit and casts a diffraction pattern on a screen 6.3 m away. The central maximum measures 1.3 cm in diameter. Determine the width of the slit in micrometres. (10.2) K/U 57. Monochromatic light passes through a single slit with a width of m. The third dark fringe (minimum) falls at an angle of 158 from the centre line. Determine the wavelength of the light in nanometres. (10.2) K/U 58. Two students use a violet laser to create a single-slit diffraction pattern on a screen 1.5 m away. The slit has a width of m. The students measure the distance from the centre of the pattern to the fifth maximum to be 6.1 cm. (10.2) T/I (a) Determine the distance between successive maxima in centimetres. (b) Determine the wavelength of the violet light in nanometres. 59. Green light has a wavelength of approximately 510 nm. When green light is diffracted through a single slit with a width of 17 mm, the observed separation of the first dark fringe and the central maximum is 2.6 cm. Determine the distance between the slit and the screen for this observation to have been made. (10.2) T/I 60. Determine the angle of the first-order maximum as red light with a wavelength of 660 nm passes through a diffraction grating with 8000 lines/cm. (10.3) T/I 61. Predict the pattern that would appear if you set two diffraction gratings in front of a laser beam. Consider the following two cases. (10.3) T/I (a) The lines on one grating are perpendicular to the lines on the other grating. (b) The lines on one grating are parallel to the lines on the other grating. 62. (a) Use the equation lm 5 w sin u m to explain why visible light cannot exhibit diffraction when reflected off crystals that have a spacing of m between the molecular planes within the crystal. (b) Discuss what type of wave will exhibit diffraction in this situation. (10.3) K/U T/I A 63. Violet light with a wavelength of 430 nm passes through a transmission grating in a spectroscope. The first-order maximum lies 168 from the centre line. (10.3) T/I (a) Determine the spacing between adjacent slits on the diffraction grating. (b) Determine the number of lines per centimetre on the diffraction grating. NEL Chapter 10 Review 553

$64. A group of students examines the diffraction pattern created when red laser light with a wavelength of 650 nm is normal upon the surface of a CD.$ 3) T/i A (a) Use both measurements to determine the average slit spacing on the CD in metres. (b) Calculate the number of lines per centimetre that are etched onto the CD.

3) T/i A (a) Use both measurements to determine the average slit spacing on the CD in metres. (b) Calculate the number of lines per centimetre that are etched onto the CD.

5 64. A group of students examines the diffraction pattern created when red laser light with a wavelength of 650 nm is normal upon the surface of a CD. The students observe a first-order maximum 348 from the centre line on one side, and the other first-order maximum is 318 from the centre on the other side. (10.3) T/i A (a) Use both measurements to determine the average slit spacing on the CD in metres. (b) Calculate the number of lines per centimetre that are etched onto the CD. (c) The CD has an etched radius of 4.0 cm, and it plays for 50 min. Determine how many rotations the CD will make if one line is read each rotation. (d) Determine the average rotational speed of the CD in revolutions per minute. 65. A beam of light with a mix of wavelengths between nm and nm passes through a transmission grating that has 2000 lines/cm. Determine the width of the first-order rainbow spectrum that appears on a screen 4.0 m behind the grating. (10.3) T/i 66. A beam of red light with a wavelength of 660 nm passes through a transmission grating with 5000 lines/cm. Determine how many maxima are present on each side of the central maximum. (Hint: The last observable maximum will appear at an angle of 908.) (10.3) T/i 67. A certain cellphone operates at a frequency of Hz. Calculate the corresponding wavelength. (10.4) T/i 68. A common remote control uses an infrared diode that emits radiation of wavelength 940 nm. (10.4) T/i (a) Determine the frequency of this radiation. (b) The remote is used to operate a television set 2.5 m away. Calculate how long it takes for the signal to reach the television. 69. A satellite TV signal operates at 89 GHz. Determine the wavelength of this signal. (10.4) T/i 70. Unpolarized light passes through two polarizing filters. The axis of the second filter is rotated 608 relative to the axis of the first filter. Determine the intensity of the transmitted light when the incoming light has intensity I in. (10.5) T/i 71. Unpolarized light passes through two polarizing filters. The transmitted light has one-tenth the intensity of the incoming light. Calculate the rotation angle of the second polarizer relative to the first. (10.5) T/i 72. Light incident at 618 in air strikes a transparent material and produces reflected light that is linearly polarized in just one direction, satisfying the condition of Brewster s angle. (10.5) k/u T/i (a) Determine the angle of reflection. (b) Determine the angle of refraction. (c) Determine the index of refraction of the material. (d) Calculate the angle of incidence that would yield completely polarized reflected light if the transparent material were water. 73. Most computer LCD projectors (Figure 5) emit polarized light of just three colours: red, green, and blue. A student projects the image of a white screen from an LCD projector. When the student holds a polarizing filter in front of the projector lens, the shadow cast by the filter is bright green. (10.5) T/i A Figure 5 (a) Explain why the shadow is green. (b) Predict what would happen if the student rotated the polarizing filter by A small incandescent bulb glows above a laboratory table. As you look directly at the bulb through a polarizer, the light is dimmed by the same amount no matter how you change the angle of the polarizer. However, as you look through the polarizer at the glare of the light bulb reflected off the shiny laboratory table, you can effectively eliminate the glare by turning the polarizer to the correct angle. Explain why the polarizer will block out the light in the second situation, but not in the first situation. (10.5) T/i A 75. When unpolarized light shines through two polarizing filters set at 908 to each other, no light will pass through. However, when a third polarizing filter is inserted between the first two at an angle of 458 relative to the first, some light will pass through all three filters (Figure 6). The original light has intensity I 0. Determine the intensity of the light that passes through all three filters. (10.5) T/i x z I I final 0 y Figure Chapter 10 Applications of the Wave Nature of Light NEL

$by another dark fringe. (10.1) K/U T/I C 77. Violet light with a wavelength of 435 nm reflects from a diffraction grating. There are 6400 lines/cm on the diffraction grating.$

6 Evaluation 76. Assess the following sentence, then rewrite or reword it to make it more accurate: The light intensity is black at the point of contact of the two plates, followed by seven bright fringes, followed by another dark fringe. (10.1) K/U T/I C 77. Violet light with a wavelength of 435 nm reflects from a diffraction grating. There are 6400 lines/cm on the diffraction grating. If you were asked to calculate how far the first-order maximum lies from the centre line, in degrees, how many significant digits would your answer have? Explain your answer. (10.3) K/U T/I 78. A classmate attempts to use an analogy to describe the polarization of light by a filter. Your classmate says, Pass a rope between two pickets of a picket fence and then try to create waves on the rope. Only waves that vibrate along the direction of the pickets will pass through the pickets. That is exactly like light polarization. Assess the accuracy of your classmate s analogy, taking into account Malus s law. (10.5) C A 79. Assess the ways in which publishing magazines and newsletters on the Internet, rather than printing and distributing them, benefits the environment. (10.4, 10.6) A Reflect on Your Learning 80. What did you find most surprising in this chapter, and what did you find most interesting? How can you learn more about these topics? K/U 81. How would you explain the concepts of thin-film interference and polarization to a fellow student who has not taken physics? K/U C 82. In what areas of your daily experience do you now see the physics concepts that were explored in this chapter? K/U A Research WEB LINK 83. Research the iridescence of colours in butterfly wings. Based on your research and findings, prepare a short oral presentation that discusses the following points: T/I C A (a) the differences between scales and cuticles. (b) the purposes of the brilliant colours in butterfly wings 84. Research the superior eyesight of a bald eagle. T/I C A (a) What is the advantage of binocular vision? (b) Describe how the fovea (a depression in the retina) is different in eagles than in humans. (c) Explain how the eyelids, eyebrows, and flexible lens also improve an eagle s vision. 85. Figure 7 shows the Very Large Array (VLA), a radio astronomy observatory in New Mexico. Research the VLA, and answer the following questions. Discuss your findings with your classmates. T/I C A Figure 7 (a) At what elevation does the VLA stand? (b) How many independent antennas are present in the observatory? (c) What is the diameter of one of these circular dishes? (d) What do astronomers observe with the VLA? (e) What are the advantages of receiving radio waves instead of other types of waves? 86. You may have seen the new QR codes on many products and posters (Figure 8). Research QR codes. T/I A Figure 8 (a) What does QR stand for? (b) Where did the QR code originate? (c) Why are QR codes becoming so popular compared with barcodes? (d) Barcodes are read by lasers. QR codes are read with cellphone cameras, but cellphone cameras do not use lasers. Why does this work? 87. Research the work and contributions of Canadian physicist and engineer Reginald Fessenden, one of the pioneers in the field of radio. What were Fessenden s notable contributions to radio and the use of radio for long-distance communication? Discuss how Fessenden s work involved using the wave model for light. Connect his work in radio to modern cellphone technology. Discuss your findings with a classmate. T/I C A NEL Chapter 10 Review 555

UNIT-5 EM WAVES UNIT-6 RAY OPTICS

UNIT-5 EM WAVES UNIT-6 RAY OPTICS UNIT-5 EM WAVES 2 Marks Question 1. To which regions of electromagnetic spectrum do the following wavelengths belong: (a) 250 nm (b) 1500 nm 2. State any one property which is common to all electromagnetic