In a medium,sound travels $2 \, km$ in $3 \, sec$ and in air,it travels $3 \, km$ in $10 \, sec$. The ratio of the wavelengths of sound in the two media is

$A$ hospital uses an ultrasonic scanner to locate tumours in a tissue. What is the wavelength of sound in the tissue in which the speed of sound is $1.7 \; km/s$? The operating frequency of the scanner is $4.2 \; MHz$.

Derive the expression for the speed of a sound wave and obtain the equations for the speed of sound in different media.

When pressure on a gaseous medium is changed at constant temperature,what will be the effect on the speed of sound wave in it?

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

$A$ train, standing in a station-yard, blows a whistle of frequency $400\,Hz$ in still air. The wind starts blowing in the direction from the yard to the station with a speed of $10\,ms^{-1}$. What will be the frequency and speed of sound for an observer? (The speed of sound in still air is $340\,ms^{-1}$)