1. 46. When you look at a distant galaxy through a telescope, are you looking backward in time?
2. 48. What is the fundamental source of electromagnetic radiation?
3. 51. Explain the principal difference between a gamma ray and an infrared ray? Defend your answer.
4. 56. Your friend says that any radio wave travels appreciably faster than any sound wave. Do you agree or disagree, and why?
5. 57. Are the wavelengths of radio and television signals longer or shorter than waves detectable by the human eye?
6. 58. Suppose a light wave and a sound wave have the same frequency. Which has the longer wavelength? How do you know this?
7. 68. Sunlight falls both on a pair of reading glasses and dark sunglasses. Which pair of glasses would you expect to become warmer? Defend your answer.
8. 79. Knowing that interplanetary space consists of a vacuum, discuss your evidence that electromagnetic waves can travel through a vacuum.
9. 81. Can you see radio waves? Can you hear radio waves? Discuss this with people who still confuse sound and radio waves.
10. 87. Lunar eclipses are always eclipses of a full Moon. That is, the Moon is always seen full just before and after Earth's shadow passes over it. Why? Why can we never have a lunar eclipse when the Moon is in its crescent or half-moon phase?
11. 36. Why do color scientists not list black and white as colors of light?
12. 40. What color does red cloth appear to be when illuminated by sunlight? By light from a red neon sign? By cyan light?
13. 43. How could you use the spotlights in a theater to change the performers' clothes suddenly from yellow to black?
14. 48. In which of these cases will a ripe banana appear blackwhen illuminated with red, yellow, green, or blue light? Defend your answer.
15. 54. our friend says that red and cyan light produce white light because cyan is green + blue, and so red + green + blue = white. Do you agree or disagree, and why?
16. 61. Comment on the statement "Oh, that beautiful red sunset is just the leftover colors that weren't scattered on their way through the atmosphere."
17. 73. Why will the leaves of a red rose be warmed more than the petals when illuminated with red light? Discuss how this relates to people in the hot desert wearing white clothes.
18. 75. The radiation curve of the Sun indicates that the brightest sunlight is yellow-green. Why then do we see the Sun as white instead of yellow-green?27.5-33 Full Alternative Text
19. 79. Why does the color black apply to pigments, but not to light?
20. 83. Why is the sky a darker blue when you are at high altitudes? (Hint: What color is the "sky" on the Moon?)