• Ch. 19: Exercises 12 & 36 12. You use a vice to firmly clamp one end of a hacksaw blade. You twang the free end and it vibrates. If you do the same, but first place a wad of clay on the free end, how, if at all, will the frequency of vibration differ? Would it make a difference if the wad of clay were stuck to the middle? Explain. (Why could this question have been asked back in Chapter 8?) 36. Why is there a Doppler effect when the source of sound is stationary and the listener is in motion? In which direction should the listener move to hear a higher frequency? A lower frequency? • Ch. 20: Exercises 18 & 50 18. As you pour water into a glass, you repeatedly tap the glass with a spoon. As the tapped glass is being filled, does the pitch of the sound increase or decrease? (What should you do to answer this question?) 50. A human cannot hear sound at a frequency of 100kHz or sound at 102kHz. But if you walk into a room in which two sources are emitting sound waves, one at 100kHz and the other at 102 kHz, you’ll hear sound. Explain. • Ch. 21: Exercises 6 & 32 6. A guitar and a flute are in tune with each other. Explain how a change in temperature could later this situation. 32. The frequency range for a telephone is between 500 Hz and 4000Hz. Why does a telephone not do a very good job of transmitting music? • Ch. 26: Exercises 8 & 38 8. We hear people talk of “ultraviolet light” and “infrared light”. Why are these terms misleading? Why are we less likely to hear people talk of “radio light” and “X-ray light”? 38. Why do objects illuminated by moonlight lack color? • Ch. 27: Exercises 10 & 16 10. The radiation curve of the Sun (Figures 27.7 and 27.8) show that the brightest light from the Sun is yellow-green. Why, then, do we see the Sun as whitish instead of yellow-green? 16. Does color television operate by color addition or by color subtraction? Defend your answer. • Ch. 28: Exercises 7 & 24 7. Why is the lettering on the front of some vehicles “backward”? 24. A pair of toy cart wheels is rolled obliquely from a smooth surface onto two plots of grass, a rectangular plot and a triangular plot as shown. The ground is on a slight incline so that, after slowing down in the grass, the wheels will speed up again when emerging on the smooth surface. Finish each sketch by showing some positions of the wheels inside the plots on the other sides, thereby indicating the direction of travel. • Ch. 29: Exercises 19 & 34 19. The colors of peacocks and hummingbirds are the result not of pigments but of ridges in the surface layers of their feathers. By what physical principle do these ridges produce colors? 34. Why do Polaroid sunglasses reduce glare, whereas nonpolarized sunglasses simply cut down the total amount of light reaching the eyes? • Ch. 30: Exercises 4 & 36 4. Ultraviolet light causes sunburns, whereas visible light, even of greater intensity, does not. Why is this so? 36. How do the avalanches of photons in a laser beam differ from the hordes of photons emitted by an incandescent lamp?
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