A bus is moving with a velocity of `5ms^(-1)` towards a huge wall . The driver sounds a horn of frequency 165 Hz . If the speed of sound in air is `335ms^(-1)` , the number of beats heard per second by a passenger inside the bus wil be

Options

A. a)3
B. b)4
C. c)5
D. d)6

Answer

C

Explanation

`f.=f((v-v_(L))/(v-v_(s)))`
`=165((355+5)/(335-5))(becausev_(L)=-5ms^(-1),v_(s)=5ms^(-1))`
`=165xx(340)/(330)`
`=170Hz`
Therefore , the number of beats heard
`=170-165=5`