Q. The wavelength of a wave is 990 cm and that of other is 100 cm. speed of sound is $396\ m/s.$ The number of beats heard is
A) 4
B) 5
C) 1
D) 8
Explanation
(a) $\Delta n = v\left\lbrack \frac{1}{\lambda_{1}} - \frac{1}{\lambda_{2}} \right\rbrack = 396\left\lbrack \frac{1}{0.99} - \frac{1}{1} \right\rbrack = 3.96 \approx 4$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.