A source of sound of frequency `256Hz` is moving rapidly towards wall with a velocity of `5m//sec`. How many beats per second will be heard if sound travels at a speed of `330m//sec`.

Answer

8

Explanation

If the second reaches the observer after being reflected from a stationary surface and the medium is also stationary,the image of the source in the reflecting surface will become the source of the reflected sound.
`f'=f_0[(v-v_0)/(v-v_s)]`
`f'=256[(330-(-5))/(330-5)]=264 therefore ` Number of beats/sec=Beat frequency=264-256-8