Question

The wavelength of two sound waves are 49 cm and 50 cm respectively. If the room temperature is ${30}^{\circ }C$ then the number of beats produced by them is approximately :
(velocity of sound in air at ${30}^{\circ }C=332m/s$)

• A. 6
• B. 10
• C. 13
• D. 18

Answer 1

The correct option is C 13

Given: speed of sound $v=332m/s$

Wavelengths of the two waves ${\lambda }_1=49cm=0.49m$ and ${\lambda }_2=50cm=0.50m$

Now ${\nu }_1=\frac{v}{{\lambda }_1}=\frac{332}{0.49}=677.55Hz$

${\nu }_2=\frac{v}{{\lambda }_2}=\frac{332}{0.50}=664Hz$

Beat frequency $b={\nu }_1-{\nu }_2=677.55-664=13.55s^{-1}$

$b\approx 13s^{-1}$