Wave Motion

Wave Motion

Wave motion is one of the most important method of transferring energy. Rather than sound energy, various forms of energies such as light, heat, X‒ray etc are transmitted by wave motion.

Example

As an example, when a stone is thrown in a pond. As soon as the stone strikes the surface of water, ripples are produced due to up & down motion of the individual particles.

This up and down motion is gradually transferred to all the neighbouring particles. So, the ripples travel outwards in the form of widening circles from the point of disturbance (or) centre.

Now, if we place a cork near the centre of disturbance at a certain distance, then, we can find that, when the ripple reaches the cork, it will simply move the cock up and down and thus the movement of cock take place.

This shows that it is only the disturbance which travels outwards while the water particles keep on moving up and down and continue to transfer the motion to the neightbouring particles. It may be noted that each particle starts vibrating a little late than its predecessor. This type on motion is called wave motion.

Definition

A wave motion can be defined as a disturbance which travels in the material medium and is due to the repeated motion of the particles in the medium, about their mean position wherein the motion is being transferred from one their mean particle to the next at regular interval of time.

Types

There are two types of waves, viz.,

(i) Transverse waves.

(ii) Longitudinal waves.

(i) Transverse waves

It is the wave motion in which the particles of the medium vibrate about their mean position perpendicular (right angles) to the direction of propagation.

Examples:

(1) Waves produced on the surface of water in which the particles of the medium vibrate up and down

(2) Waves produced in stretched strings.

Note: Tranverse wave cannot travel in a gas, because cohesion is absent in gases.

(ii) Longitudinal waves

It is the wave motion in which the particles of the medium vibrate about their mean position along the same line as that of propagation of the wave.

Examples:

(1) Condensation & rarefactions produced in air by the vibratory motion of a tuning fork.

(2) Compressions & rarefactions in air when one end is fixed & other end is moved with piston in a cylinder [Kundt's tube experiment].

DIFFERENCES BETWEEN TRANSVERSE & LONGITUDINAL