Question

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

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

Answer 1

Answer: (C)

660 Hz

Answer 2

From $\Delta x=\frac{\lambda}{2\pi} \Delta \phi,$
$\lambda=2\pi\frac{\Delta x}{\Delta \phi}=\frac{2\pi(0.4)}{1.6 \pi}=0.5\,m$
$\upsilon =\frac{v}{\lambda}=660\, Hz$