Question

Velocity of sound waves in air is $330 \,m/s$. For a particular sound in air, a path difference of $40 \,cm$ is equivalent to phase difference of $1.6\pi$ The frequency of the wave is

• A. 165 Hz
• B. 150 Hz
• C. 660 Hz
• D. 330 Hz

Answer 1

Answer: (C)

Phase difference $=\frac{2 \pi}{\lambda} \times$ path difference
$1.6 \pi=\frac{2 \pi}{\lambda} \times 40$
$\lambda=\frac{2}{16} \times 40=50 \,cm =0.5\, m$
$v=v \lambda, $
$v=$ Velocity of sound
$v=\frac{u}{\lambda}, $
$v=$ Frequency
$=\frac{330}{0.5}=660\, Hz$