A plane flies toward a stationary siren at 1/4 the speed of sound. Then the plane stands still on the ground and the siren is driven toward it at 1/4 the speed of sound. In both cases, a person sitting in the plane will hear the same frequency of sound from the siren.

Question

Quizplus · Accepted Answer

The Doppler effect depends on the relative motion between the source and the observer. When the plane moves towards the stationary siren, the frequency increases due to the plane's motion. When the siren moves towards the stationary plane, the frequency also increases, but the effect is not identical because the source and observer roles are reversed, leading to different frequency shifts.

A Plane Flies Toward a Stationary Siren at 1/4 the Speed