With what velocity should an observer approach a stationary shound source so that the apparent frequency of shound should appear double the actual frequency ? (v is velocity of shound).

Options

A. 2v
B. v
C. `v//2`
D. 3v

Answer

B

Explanation

`v_(obs)=v_("emitted")(("vel . if sound + vel . of observer"))/("vel . of sound")`
For the observed frequency change due to Doppler effect.
`v_("obs")"will be "2v_("emtted")` if velocity of the observer is equal to the velocity of sound.