Which of the following could give rise to the Doppler Effect?

Question

Which of the following could give rise to the Doppler Effect?

A. Either the source of sound and/or the listener is/are moving.

B. Both the source of sound and the listener must be moving.

C. The source of sound is stationary and the listener must be moving.

D. The source of sound must be moving and the listener must be stationary.

Answer 1

The Doppler effect is described by f_r = [(v +/- v_r)/(v +/- v_s)]f_s, where f_r and f_s are the frequencies of the receiver and the source, respectively, and v_r and v_s are the velocities of the receiver and the source, respectively, and v is the speed of sound. As you can see, the Doppler Effect can be due to either only the source moving or only the receiver moving or both source and receiver moving. Only one of the velocities v_r and v_s must be non-zero in order to obtain a Doppler shift in the frequency.