Page 202 - Schaum's Outline of Theory and Problems of Applied Physics

CHAP. 15] WAVES AND SOUND 187

7
Here the galaxy is receding, so v =−6.1 × 10 m/s and
1/2
7 8
1 − (−6.1 × 10 m/s)(3 × 10 m/s)
λ = (5.5 × 10 −7 m/s)
7
8
1 + (−6.1 × 10 m/s)(3 × 10 m/s)
1/2
1 + 0.203

= (5.5 × 10 −7 m)
1 − 0.203
= 8.3 × 10 −7 m

Multiple-Choice Questions

15.1. The lower the frequency of a wave,
(a) the higher its velocity (c) the smaller its amplitude
(b) the longer its wavelength (d) the shorter its period
15.2. An entirely longitudinal wave is

(a) a water wave (c) an electromagnetic wave
(b) a sound wave (d) a wave in a stretched string

15.3. Sound cannot travel through a
(a) vacuum (c) liquid
(b) gas (d) solid

15.4. Of the following properties of a wave, the one that is independent of the others is its
(a) velocity (c) frequency
(b) wavelength (d) amplitude

15.5. When a sound wave goes from air into water, the wave property that does not change is its
(a) velocity (c) frequency
(b) wavelength (d) amplitude
15.6. The wavelength of 400-Hz sound waves in air relative to the wavelength of 800-Hz sound waves in air is
(a) half as long (c) twice as long
(b) the same (d) 4 times as long

15.7. A spacecraft is approaching the earth. Relative to the radio signals it sends out, the signals received on the earth have
(a) a lower frequency (c) a higher velocity
(b) a shorter wavelength (d) all of the above

15.8. A radio station broadcasts at a frequency of 660 kHz. The wavelength of these waves is
(a) 2.2 mm (c) 4.55 km
14
(b) 455 m (d) 1.98 × 10 m
15.9. Waves whose crests are 30 m apart reach an anchored boat once every 3.0 s. The wave velocity is
(a) 0.1 m/s (c) 10 m/s
(b) 5 m/s (d) 900 m/s