Question

Sound waves in air are
$\text{A}\text{. transverse}$
$\text{B}\text{. longitudinal}$
$\text{C}\text{. electromagnetic}$
$\text{D}\text{. polarised}$

Answer 1

Hint: Sound wave in any medium is the consequence of back and forth vibrations of medium particles in the direction of motion of wave. Sound waves travel in the form of compressions and rarefactions of small volume elements of the medium.

Complete step-by-step answer:
Sound wave is a mechanical wave that is produced as a consequence of back and forth vibration of the particles of the medium through which the sound wave travels.
Longitudinal waves are the waves in which particle displacement is parallel to the direction of wave propagation. The particles do not travel along, they just move back and forth about their equilibrium positions.
In a transverse wave the particles are displaced perpendicularly to the direction of wave propagation. Particles simply oscillate up and down about their equilibrium positions.
Electromagnetic waves also known as EM waves are waves produced as a consequence of vibrations between an electric and a magnetic field. EM waves travel with a constant velocity of $3\times {{10}^{8}}m{{s}^{-1}}$. Light is an EM wave.
Polarised light waves are light waves in which the vibrations occur in a single plane. Actually polarisation is a property of transverse waves that specifies the geometric orientation of the oscillations.
We can now conclude that sound waves are longitudinal waves because in sound waves, particles vibrate to and fro about their mean position in the direction of propagation of waves which is the property of longitudinal waves.

So, the correct answer is “Option B”.

Note: In transverse waves, particles vibrate perpendicular to direction of motion. Therefore sound waves are not transverse waves.
As sound waves cannot travel without any medium they are also not electromagnetic waves which can propagate in vacuum also.