Question

A source of sound is moving with a velocity of 50 ms^-1 towards a stationary observer. The observer measures the frequency of sound as 500 Hz. The apparent frequency of sound as heard by the observer when source is moving away from him with the same speed is (Speed of sound at room temperature 350 ms^-1 ) 

(1) 666 Hz 

(2) 177.5 Hz 

(3) 400 Hz 

(4) 375 Hz 

Answer 1

Correct option (4) 375 Hz

Explanation:

vL = 0, vs = -50 ms^-1 , fapp = 500 Hz (source towards the listener)

f app?  (source away from the listener) 

v = v_sound = 350 ms^-1

• Case (i): Source towards the listener

• Case (ii): Source away from the listener