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 a phase difference of $1.6\, \pi$. The frequency or the wave is:

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

Answer 1

Answer: (C)

660 Hz

Answer 2

Phase difference of $1.6\, \pi$ corresponds to path difference of $40\, cm$. Hence, phase difference of $2 \pi$ will correspond to a path difference of $50\, cm$, i.e., $\lambda=50\, cm$ or $0.5\, m$. $\therefore n =\frac{v}{\lambda}=\frac{330}{0.5}$ $=660\, Hz$