Question

Which of the following factors by itself will increase the frequency at which an observer hears a sound emanating from a source?

• A. A wind blows from the source to the observer
• B. The source and the observer move away from each other at the same speed
• C. The source and the observer move in the same direction at the same speed
• D. The source moves away from the observer more slowly than the observer moves toward the source

Hint:

The Doppler effect causes an increase in frequency when the observer and source are moving toward each other.

Answer 1

The Correct Option is D

The frequency at which an observer hears sound from a moving source is affected by the Doppler effect.
The observed frequency increases when the observer is moving toward the source or when the source is moving toward the observer.
In this case, if the observer moves toward the source while the source is moving away from the observer more slowly, the frequency will increase.
Thus, the correct answer is (d).