An engine is moving on a circular path of radius 100 m with a speed of 20 m/s. What will be frequency noted by an observer standing stationary at the centre of the circular path when the engine blows a whistle of frequency 500 Hz ?

Options

A. more than `500Hz`
B. less than `500Hz`
C. `500Hz`
D. no sound is heard

Answer

C

Explanation

The line joining observer and source is perpendicular to `v_(s)` and hence doppler effect is not applicable.
`:.n.=n=500Hz`