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. 1330 Hz
B. 1140 Hz
C. 750 Hz
D. 850 Hz

Answer

C

Explanation

Apparent frequency
`n =((v)/(v-v_(s))n)`
`rArr " " 1000 =(350)/(350-50) xx n`
or `n= (3000)/(35)`
when the source is moving away form the observer, then the new
`n = ( (v)/(v+v))n`
`=(350)/(350+50) xx (3000)/(35)`
`=750 Hz`