Question

Two sound waves of wavelengths 5m and 6m formed 30 beats in 3sec. The velocity of sound is

• A. 300 m/s
• B. 310 m/s
• C. 320 m/s
• D. 330 m/s

Answer 1

The correct option is A 300 m/s

$Beats={\delta }_1-{\delta }_2=\frac{30}{3}$ -------- (1)

${\delta }_1=\frac{v}{{\lambda }_1}$ and ${\delta }_2=\frac{v}{{\lambda }_2}$

From (1):
$\frac{v}{{\lambda }_1}-\frac{v}{{\lambda }_2}=10$

$v(\frac{1}{5}-\frac{1}{6})=10$

$v=\frac{5\times 6\times 10}{6-5}=300m/s$