Q. Two sound waves of wavelengths $5m$ and $6m$ formed 30 beats in 3 seconds. The velocity of sound is
A) $300\ ms^{- 1}$
B) $310\ ms^{- 1}$
C) $320\ ms^{- 1}$
D) $330\ ms^{- 1}$
Explanation
(a) No of beats, $x = \mathrm{\Delta}n = \frac{30}{3} = 10\ Hz$
$\Rightarrow$ Also $\mathrm{\Delta}n = v\left\lbrack \frac{1}{\lambda_{1}} - \frac{1}{\lambda_{2}} \right\rbrack = v\left\lbrack \frac{1}{5} - \frac{1}{6} \right\rbrack = 10 \Rightarrow v = 300\ m/s$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.