Question

A sound wave of wavelength $4\text{mm}$ is produced in air, and it travels at a speed of $300\text{m/s}$. Will it be audible?

• A. Yes
• B. No
• C. Sometimes audible & sometimes inaudible
• D. Can't say

Answer 1

The correct option is B No

We know that velocity of sound wave is given by,
$v=\lambda f$, where $\lambda$ is wavelength and $f$ is frequency.
$\Rightarrow f=\frac{v}{\lambda }$
$\Rightarrow f=\frac{300}{4\times {10}^{-3}}$
$\Rightarrow f=75\text{kHz}$
We know audible range of human ear is $20\text{Hz}-20\text{kHz}$.
As frequency of this sound is out of this range, therefore it will not be audible.