A car sounding its horn at `480Hz` moves towards a high wall at a speed of `20ms^(-1)`, the frequency of the reflected sound heard by the man sitting in the car will be nearest to , (speed of sound `=330m//s)`

Options

A. 480 Hz
B. 510 Hz
C. 540 Hz
D. 570 Hz

Answer

A

Explanation

Here, `v_(s)=20m//s, v=340m//s, upsilon=480Hz`
As source is moving towards the wall and wall acts as observer, apparent frequency of sound striking the wall is
`upsilon.=(vxxupsilon)/(v-v_(s))=(340xx480)/(340-20)=510Hz`
On reflection, wall acts as source and man sitting in the car is observer. It is moving towards the wall.
`therefore upsilon..=((v+v_(o))upsilon.)/(v)=((340+20)510)/(340)=540Hz`