1. Wave Motion:

a) The sound waves can also be called as elastic waves and medium is needed for their propagation. Their velocity is different for different media.

b) The velocity of sound waves depends on the property of inertia and coefficient of elasticity of that medium.

c) In this type of motion the energy is transferred from one point to other by the propagation of disturbance in the medium. The motion of disturbance is called the wave motion.

d) In simple harmonic wave the particles of the medium executes simple harmonic motion. Each particle of the medium executes simple harmonic motion at all the times, though the phase of its vibration depends on its position and time.

On the basis of vibration of the particle waves are classified in two types:

(a)   Transverse waves.

(b)   Longitudinal waves.
(a) Transverse waves:

The particles of medium vibrate in a direction perpendicular to the direction of propagation of wave. Their polarization is possible. Example: Vibration of string, the surface waves produced on the surface of solid and liquid.

    Fig (1)
(b) Longitudinal waves:

Vibrations of the particles of the medium are in the direction of wave propagation wave proceeds in form of compression and rarefaction. At places of compression the pressure and density are maximum, while at places of rarefaction those are minimum.

Example: Sound waves, waves is gases, waves is solids.

                                                 Fig (2)