A speed ign motorcyclist sees traffic ham ahead of him. He slows doen to `36 km//h` He finds that traffic has eased and a car moving ahead of him at `18 km//h` is honking at a frequency of 1392 Hz. If the speed of sound is `343m//s`, the frequency of the honk as heard by him will be

Options

A. `1332 Hz`
B. `1372 Hz`
C. `1412 Hz`
D. `1454 Hz`

Answer

C

Explanation

`v_0=36 km//h =10m//s`
`v_S=18km//h =5m//s`

`f'=f[(upsilon+upsilon_0)/(upsilon+upsilon_S)]=1392xx((342+10)/(342+5))Hz`
`=1392xx(352)/(348)Hz=1412Hz`