Question

When a train, blowing its whistle, approaches him, the pitch of the whistle appears to rise and it appears to drop as the engine moves away from him. What is the effect observed here?

(a) Doppler effect

(b) Frequency effect

(c) Beats

(d) Echelon effect

This question was posed to me in class test.

Origin of the question is Reverberation topic in chapter Waves of Engineering Physics I

Answer 1

Correct option is (a) Doppler effect

Explanation: Whenever there is a relative motion between the source, the observer and the medium, the frequency of sound emitted by the source as received by the observer is different from the frequency of sound emitted by the source. The apparent change in frequency when the source, the observer and the medium are in motion is called Doppler effect.