Question

Two sound waves with wavelengths $5.0\, m$ and $5.5.\, m$ respectively, each propagate in a gas with velocity $330\, m/s$. We expect the following number of beats per second :-

• A. 6
• B. 12
• C. 0
• D. 1

Answer 1

Answer: (A)

Frequency $=\frac{\text { velocity }}{\text { wavelength }}$
$\therefore v_{1}=\frac{v}{\lambda_{1}}=\frac{330}{5}=66\, Hz$
and $v_{2}=\frac{v}{\lambda_{2}}=\frac{330}{5.5}=60\, Hz$
Number of beats per second $=v_{1}-v_{2}$
$=66-60=6$.