A source of sound S is moving with a velocity of `50m//s` towards a stationary observer. The observer measures the frequency of the source as 1000 Hz. What will be the apparent frequency of the source as 1000 Hz. What will be the apparent frequency of the source when it is moving away from the observer after crossing him? The velocity of the sound in the medium is `350m//s`

Options

A. 1143Hz
B. 857Hz
C. 750Hz
D. 807Hz

Answer

C

Explanation

`f_(ap) = f((350)/(350 - 50)) = 1000`
`f_(ap) ' (after crossing)
= f((350)/(350 + 50))= (1000 xx 3000)/(350) xx (350)/(450) = (3000)/(4) 750Hz`