$A$ plane wave of sound traveling in air is incident upon a plane surface of a liquid. The angle of incidence is $60^{\circ}.$ The speed of sound in air is $300 \, m/s$ and in the liquid it is $600 \, m/s.$ Assume Snell's law to be valid for sound waves.

$A$ 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 .... $m$

Earthquakes generate sound waves inside the earth. Unlike a gas,the earth can experience both transverse $(S)$ and longitudinal $(P)$ sound waves. Typically,the speed of $S$ wave is about $4.0 \; km/s$,and that of $P$ wave is $8.0 \; km/s$. $A$ seismograph records $P$ and $S$ waves from an earthquake. The first $P$ wave arrives $4 \; min$ before the first $S$ wave. Assuming the waves travel in a straight line,at what distance (in $km$) does the earthquake occur?

What is called compression or condensation? Which type of changes in density and pressure take place in it?

At what temperature does the velocity of sound in air increase by $10\%$ compared to its velocity at $0^{\circ}C$ (in $^{\circ}C$)?

Write the equation for the speed of a sound wave in metals.