Q.
A small source of sound moves on a circle as shown in the figure and an observer is standing on $O.$ Let $n_{1},n_{2}$ and $n_{3}$ be the frequencies heard when the source is at $A,\ B\ $ and $C$ respectively. Then
A) $n_{1} > n_{2} > n_{3}$
B) $n_{2} > n_{3} > n_{1}$
C) $n_{1} = n_{2} > n_{3}$
D) $n_{2} > n_{1} > n_{3}$
Explanation
(b) At point $A,$ source is moving away from observer so apparent frequency $n_{1} < n$ (actual frequency) At point $B$ source is coming towards observer so apparent frequency $n_{2} > n$ and point $C$ source is moving perpendicular to observer so $n_{3} = n$
Hence $n_{2} > n_{3} > n_{1}$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.