Question

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

• A. $\frac{v}{2}$
• B. $3v$
• C. $2v$
• D. $v$

Answer 1

Answer: (D)

$v$

Using above equation for apparent frequency

given $V_s=0,f_{app}=2f$ where $f$ is actual frequency and $V$ is velocity of sound

By substituting above given values we get

$2f=f\frac{V+V_o}{V}$

$\Rightarrow 2V=V+V_o$

$\Rightarrow V_o=V$