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38. Green grass reflects 49. The special theory of relativity is
a. yellow light. a. a new explanation of gravity.
b. green light. b. an analysis of how space and time are changed by motion.
c. blue light. c. an analysis of how fast-moving clocks run faster.
d. white light. d. based on a changing velocity of light.
39. Green grass absorbs 50. The general theory of relativity explains
a. yellow light. a. gravity as a change of space and time.
b. only green light. b. why the speed of light changes with the speed of an observer.
c. blue light. c. how the laws of physics change with changes of motion.
d. all light but green light. d. Newton’s laws of motion.
40. We see a blue sky because 51. Comparing measurements made on the ground to measurements
a. air molecules absorb blue light. made in a very fast airplane would find that
b. air molecules reflect red light. a. the length of an object is shorter.
c. scattering of light by air molecules and dust is more efficient b. clocks run more slowly.
when its wavelength is longer. c. objects have an increased mass.
d. scattering of light by air molecules and dust is more efficient d. all of the above are true.
when its wavelength is shorter.
Answers
41. A pencil is placed in a glass of water. The pencil appears to be
1. c 2. c 3. b 4. b 5. d 6. c 7. b 8. b 9. b 10. c 11. c 12. c 13. a
bent. This is an example of
14. c 15. a 16. a 17. b 18. c 19. b 20. c 21. c 22. b 23. a 24. c
a. reflection.
25. d 26. c 27. d 28. a 29. c 30. b 31. a 32. c 33. d 34. b 35. d
b. refraction.
36. d 37. a 38. b 39. d 40. d 41. b 42. c 43. b 44. a 45. d 46. b
c. dispersion.
47. c 48. b 49. b 50. a 51. d
d. polarization.
42. A one-way mirror works because it
a. transmits all of the light falling on it. QUESTIONS FOR THOUGHT
b. reflects all of the light falling on it.
c. reflects and transmits light at the same time.
1. What determines if an electromagnetic wave emitted from an
d. neither reflects nor transmits light.
object is a visible light wave or a wave of infrared radiation?
43. A mirage is the result of light being
2. What model of light does the polarization of light support?
a. reflected.
Explain.
b. refracted.
3. Which carries more energy, red light or blue light? Should this
c. absorbed.
mean anything about the preferred color of warning lights and
d. bounced around a lot.
stoplights? Explain.
44. A glass prism separates sunlight into a spectrum of colors because
4. What model of light is supported by the photoelectric effect?
a. shorter wavelengths are refracted the most.
Explain.
b. light separates into colors when reflected from crystal glass.
5. What happens to light that is absorbed by matter?
c. light undergoes absorption in a prism.
d. there are three surfaces that reflect light. 6. One star is reddish and another is bluish. Do you know anything
about the relative temperatures of the two stars? Explain.
45. Polaroid sunglasses work best in eliminating glare because
a. reflected light is refracted upward. 7. When does total internal reflection occur? Why does this occur
b. unpolarized light vibrates in all possible directions. in the diamond more than other gemstones?
c. reflected light undergoes dispersion. 8. Why does a highway sometimes appear wet on a hot summer day
d. reflected light is polarized in a horizontal direction only. when it is not wet?
46. The condition of farsightedness, or hyperopia, can be corrected 9. How can you tell if a pair of sunglasses is polarizing or not?
with a (an) 10. What conditions are necessary for two light waves to form an
a. concave lens. interference pattern of bright lines and dark areas?
b. convex lens.
11. Explain why the intensity of reflected light appears to change if
c. eyepiece lens.
you tilt your head from side to side while wearing polarizing
d. combination of convex and concave lenses.
sunglasses.
47. Today, light is considered to be a stream of photons with a
12. Why do astronauts in orbit around Earth see a black sky with
frequency related to its energy. This relationship finds that
stars that do not twinkle but see a blue Earth?
a. frequencies near the middle of the spectrum have more energy.
13. What was so unusual about Planck’s findings about blackbody
b. more energetic light is always light with a lower frequency.
radiation? Why was this considered revolutionary?
c. higher-frequency light has more energy.
d. lower-frequency light has more energy. 14. Why are both the photon model and the electromagnetic wave
model accepted today as a single theory? Why was this so
48. An instrument that produces a coherent beam of single-
difficult for people to accept at first?
frequency, in-phase light is a
a. telescope.
b. laser.
c. camera.
d. solar cell.
7-25 CHAPTER 7 Light 201