With what velocity an observer should move relative to a stationary source so that he hears a sound of double the frequency of source?

Options

A. Velocity of sound towards the source
B. Velocity of sound away from the source
C. Half the velocity of sound towards the source.
D. Double the velocity of sound towards the source.

Answer

A

Explanation

`n' =n((v)/(v-v_S))`
`2n=n((v-v_0)/(v-0))impliesv_O=-v=-`(speed of sound)
Negative sign indicates that observer is moving opposite to the direction of velocity of sound, as shown