Q. An observer is approaching a stationary source with a velocity $1/4\ $th of the velocity of sound. Then the ratio of the apparent frequency to actual frequency of source is
A) 4:5
B) 5:4
C) 2:3
D) 3:2
Explanation
(b) When an observer is moving towards the source apparent frequency
$n^{'} = n \times \left( \frac{v + v_{o}}{v} \right)$
Or
$n^{'} = n \times \frac{4}{4}$
Or
$\frac{n^{'}}{n} = \frac{5}{4}$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.