Question

a train moving at a speed of 20 ms-1 towards a station sounding a whistle of frequency 500 Hz calculate the apparent frequencies of the whistle as heard by the man standing on the platform a) approaches him ,b)reaches him​

Answer 1

Explanation:

This is the Doppler's shift.

 

Apparent frequency= f.

v = velocity of sound = 330 m/s

Frequency of the sound source = f₀ = 600 Hz

Velocity of the source (train) = Vs = + 72 kmph = +20 m/s

velocity of the observer = Vo = 0 

When the train approaches, the frequency will be more and it will be less as the train goes away.