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

Question

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

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

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

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

Answer 1

For Doppler effect to be applicable there must be a relative motion between the source of the sound and the listener of the sound.

In A., B. and C we can clearly see there is a relative motion between the source of soud and the listener. So, doppler effect is all these 3 cases can be felt.

In case of D. while both the source and listener are moving we do not know the speed and the direction of their motion. If both are moving in the same direction with same speed then there is zero relative movement between the source and the listener causing NO Doppler effect. But if either the direction of the motion or the speed of the motion or both are different for the source of sound and the lsiener then there would be Doppler effect.