Question

Two sound waves with wavelengths $5.0\text{m}$ and $5.5\text{m}$ respectively, each propagates in a gas with velocity $330\text{m/s}$. Number of beats heard per second is

• A. $6$
• B. $12$
• C. $0$
• D. $1$

Answer 1

The correct option is A $6$

We know that,
Frequency $=\frac{\text{velocity}}{\text{wavelength}}$
Frequency of first wave is
$\therefore v_1=\frac{v}{{\lambda }_1}=\frac{330}{5}=66\text{Hz}$ and
Frequency of second wave is
$v_2=\frac{v}{{\lambda }_2}=\frac{330}{5.5}=60\text{Hz}$
Number of beats heard per second $=v_1-v_2$
$=66-60=6\text{Hz}.$
Hence, the correct answer is option (a).