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

Options

A. 3
B. 4
C. 5
D. 6

Answer

C

Explanation

Apparent frequency, `v'=v ((v+v_(o))/(v-v_(s)))=165 ((335+5)/(335-5))`
`( :' v_(0)=5 ms^(-1), v_(s)=5 ms^(-1))`
`=165 xx340/330=170` Hz
Therefore, the number of beats heard `=170-165=5`