A source of sound is moving with a velocity of `50ms^(-1)` towards a stationary listener. The listener measures the frequency of the source as 1000Hz. What will be the apparent frequency of the source when it is moving away from the listener after crossing him? (velocity of sound in the medium is `330ms^(-1)`).

Explanation

When the source is moving towards the stationary listener, the expression for apparent frequency is
`n. = (v/(v-v_s))n,`
`1000 = (330/(330-50))n`
`n = ((1000 xx 280)/330)`
n = 848.48 Hz.
The actual frequency of the sound is 848.48 Hz. When the source is moving away from the stationary listener, the expression for apparent frequency is
`n. = (v /(v-v_s))n`
`= (330/(330 + 50))xx 848. 48 = 736.84 Hz`.