Q. A source of sound of frequency 256 Hz is moving towards a wall with a velocity of $5ms^{- 1}$. Velocity of sound is $330{ms}^{- 1}$.The number of beats $s^{- 1}$ heard by an observer standing between the source and the wall is nearly
A) $\frac{256 \times 330}{325} - \frac{256 \times 330}{325}$
B) $256 - \frac{256 \times 330}{325}$
C) $\frac{256 \times 330}{325} \times \frac{256 \times 330}{335}$
D) $\frac{256 \times 330}{325} - 256$
Explanation
(a) No beat is heard, because frequency received by listener directly from the source and that received on reflection from the wall is same
$= \frac{256 \times 330}{330 - 5}\ Hz$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.