Answers and Explanations

Review Questions

1. C
   The wavelength is the length of one full cycle.
2. A

   The amplitude is half the distance from trough to crest, or

   
3. C

   The wave vibrates two times per 0.4 s, so the frequency is

   
4. C
   The frequency is and the speed v = f λ = (2 Hz)(0.5 m) = 1.0 m/s.
5. B
   The pitch of a moving sound source sounds higher if it is moving toward you, and lower if it is moving away from you.
6. E
   A wave will travel faster in a tight spring than a loose spring.
7. C
   The center of the wave passes through the opening while the edges of the wave drag on the sides of the opening.
8. B
   When both waves are exactly between P and Q, one wave’s trough is superposed on the other wave’s crest, causing the waves to interfere destructively, canceling each other out.
9. D
   The wavelength is the length of two loops and is 1 m. The speed of the wave is v = f λ = (60 Hz)(1 m) = 60 m/s.