What should be the velocity of a sound source moving towards a stationary observer so that apparent frequency is double the actual frequency (Velocity of sound is v)
Correct option is C. $$\dfrac{v} {2}$$
By using $$ n' = \left ( \dfrac{v } {v - v_s} \right )$$
$$ \Rightarrow 2n = n = \left ( \dfrac{v } {v - v_s} \right ) $$
$$\Rightarrow v_s = \dfrac{v} {2}$$