The intensity of sound increases at night due to

Find the wavelength of a sound wave of frequency $4.2 \text{ MHz}$ travelling with a speed of $1.7 \text{ km/s}$.

Write the equation for the speed of a sound wave according to Newton and explain the correction made by Laplace.

The frequency of a sound wave is $n$ and its velocity is $v$. If the frequency is increased to $4n$,the velocity of the wave will be

Velocity of sound in vacuum is .... $ms^{-1}$

$A$ man,standing between two cliffs,claps his hands and starts hearing a series of echoes at intervals of one second. If the speed of sound in air is $340 \, ms^{-1}$,the distance between the cliffs is .... $m$