Question

A source of sound emitting a tone of frequency 200 Hz moves towards an observer with a velocity v equal to the velocity of sound if the observer also moves away from the source with the same velocity v, the apparent frequency heard by the observer is

• A. $50Hz$
• B. $100Hz$
• C. $150Hz$
• D. $200Hz$

Answer 1

Answer: (D)

$200Hz$

The frequency of sound is $f_s=200Hz$

The velocity of sound and velocity of the observer are same. And both are moving in the same direction

(Relative velocity) $v_r=0$

So, there is no Doppler effect and thus observer observes the same frequency.

$f_0=F_s=200Hz$

Thus, option (d) is correct.