Q. Two trains, one coming towards and another going away from an observer both at $4\ m/s$ produce whistle simultaneously of frequency $300\ Hz.$ Find the number of beats produced
A) 5
B) 6
C) 7
D) 12
Explanation
(c) $\mathrm{\Delta}n = \left\lbrack \frac{v}{v - u} - \frac{v}{v + u} \right\rbrack n = \frac{2uv}{v^{2} - u^{2}}n$
$= \frac{2 \times 4 \times 332}{(332)^{2} - (4)^{2}} \times 300 = 7$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.