Light waves can be polarised but sound waves cannot be. Why?

Explanation

Because light waves are transverse in nature while sound waves are longitudinal. Polarisation of wave means separation of vibrations taking place in one direction from the vibrations taking place in all directions in a plane perpendicular to the direction of the wave. In a longitudinal wave the vibration cannot separate out in one particular direction perpendicular to the direction of propagation. Therefore polarisation is never observed in sound waves.