Q. A sound wave of frequency v propagating through air with a velocity c, is reflected from a surface which is moving away from the source with a constant speed v. the frequency of the reflected wave, measured by the observed at the position of the source, is
A) $\frac{v(c - v)}{c + v}$
B) $\frac{v(C + v)}{c - v}$
C) $\frac{v(c + 2v)}{c + v}$
D) $\frac{v(c - v)}{c - 2v}$
Explanation
(c) In our case both source and observer are moving, so perceived frequency
$v^{'} = \frac{v\left( c - v_{o} \right)}{\left( c - v_{s} \right)}$
Where $v_{o}\ is$ the velocity of observer, $v_{s}$ is the velocity of source and c is velocity of sound.
Given,
$v_{o} = - 2v,\ v_{s} = - v$
$\therefore v^{'} = \frac{v(c + 2v)}{(c + v)}$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.