Chapter 14, Problem 43PCE

Predict/Explain A horn produces sound with frequency f₀, Let the frequency you hear when you are at rest and the horn moves toward you with a speed u be f₁ let the frequency you hear when the horn is at rest and you move toward it with a speed u be f₂. (a) Is f₁ greater than, less than, or equal to f₂? (b) Choose the best explanation from among the following:

1. I. A moving observer encounters wave crests more often than a stationary observer, leading to a higher frequency.
2. II. The relative speeds are the same in either case. Therefore, the frequencies will be the same as well.
3. III. A moving source causes the wave crests to “bunch up,” leading to a higher frequency than for a moving observer.