Question

A car is moving with a velocity of `5 m//s` towards huge wall. The driver sounds a horn of frequency `165 Hz`. If the speed of sound in air is `335 m//s`, the number of beats heard per second by the driver is
A. `6`
B. `5`
C. `4`
D. `3`

Answer 1

Correct Answer - B
Frequency of reflected sound
`f_(r ) = f((v+u)/(v-u)) = 165((335+5")/(335-5)) = 170 Hz`
Beta freuqency `= f_(r) - f = 170 - 165 = 5 Hz`