A siren emiting sound of frequency `800Hz` is going away from a static listence with a speed of `30 m//s`frequency of sound to be beand by the listener is `("velocity of sound" = 330 m//s)`

Options

A. `286.5 Hz`
B. `481.2 Hz`
C. `733.3Hz`
D. `644.8Hz`

Answer

c

Explanation

The appared change in the frequency of the source that to relative motion between source and abserve known as Dippler's effect . The percaived frequency `(n')` when listener is state and nature is moving away is given by
`n^(1) = n((v)/(v + v_(s))),`
where n is frequency of source v is velocity sound and `v_(s)` is velocity of source
Putting `v = 330 m//s , v_(s) = 30 m//s , n = 800 Hz`
`n' = 800 xx ((330)/(330 + 30))`
In the limit speed of source and observer are much leser than that of sound `v_(s)` the change in frequency become independent of the face whether the source is moved or the detector.