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

Answer

`7.87 Hz`

Explanation

Frequency reaching the wall `f_(1)=f_(0)((v)/(v-v_(s)))`
Frequency received by the observer
`f_(1)=f_(1),((v+v_(s))/(v))=f_(0)((v+v_(s))/(v-v_(s)))`
`:.` Beat frequency
`Delta f=f_(0)((v+v_(s))/(v-v_(s)))-f_(0)=256((330+5)/(330-5))-256`
`=7.87 Hz`