A sound source is moving with speed `50 m//s` towards a fixed observer. Frequency observed by observer is `1000Hz`. Find out apparent frequency observed by observer when source is moving away from observer (Speed of sound `=350 m//s`)

Options

A. 750 Hz
B. 857 Hz
C. 1143 Hz
D. 1333 Hz

Answer

A

Explanation

When the source is coming to stationary observer,
`n'=((v)/(v-v_S))n`
or `1000=((350)/(350-50))n`
or `n=(1000xx(300)/(350))Hz`
when the source is moving away from the stationary observer.
`n''=((v)/(v+v_S))n`
`=((350)/(350+50))((1000xx300)/(350))=750Hz`