Question

At what speed should a source of sound move so that stationary observer finds the apparent frequency equal to half of the original frequency?

• A. $\frac{v}{2}$
• B. $2v$
• C. $\frac{v}{4}$
• D. $v$

Answer 1

The correct option is D $v$

Here, frequency $n^{\prime }=\frac{n}{2}$
We have, $\frac{n}{2}=n\left(\frac{v}{v+v_s}\right)$
or $\frac{v+v_s}{v}=2$
or $v_s=v$