Mechanical Waves : Definition, Properties and Characteristics

Many modern technologies, such as computers and smartphones, are built on the principles of Physics Topics such as quantum mechanics and information theory.

What is a Wave Simple Definition?

When a small piece of stone is thrown into a ponds, the water surface gets disturbed. The ripples formed due to this disturbance do not remain confined to the region where the stone hits the water surface, but it spreads in all directions along the surface. As the disturbance passes, the water particles start oscillating i.e., moving up and down about their mean positions but are not displaced along the water surface. The pattern that moves along the pond due to such movement of individual particles of the medium, is called a wave. This wave motion transfers energy from one point to another, but no mass transport is associated with this transfer.

Wave: Wave is a disturbance that travels through a medium, whereas the particles constituting the medium do not travel.

We are familiar with different types of waves; like sound waves, light waves, radio waves, etc. Among these, sound wave is a mechanical wave and the other two are electromagnetic waves. In this chapter, we are mainly concerned with mechanical waves. Mechanical waves can propagate only through a material medium, whereas electromagnetic waves do not require any material medium for propagation, i.e., they can propagate through vacuum.

Mechanical Waves

The origin and propagation of mechanical waves depend on three properties of materials—

1. elasticity,
2. inertia and
3. cohesion.

1. Elasticity: If any part of a material or a medium is displaced from its equilibrium position, a stress is developed in it due to its elasticity. This stress tries to bring that part back to its equilibrium position.

2. Inertia: When a particle returns to its equilibrium position, it has a motion due to inertia. So the particle cannot come to rest immediately on reaching the equilibrium position. Due to inertia of motion, it moves to the opposite side crossing the equilibrium position. These two incidents—coming back to the equilibrium position due to elasticity and moving to the opposite side due to inertia of motion—happen alternately in any part of a material or a medium, causing that part to vibrate.

Definition: The disturbance which travels through a material medium, due to collective vibration of the particles of the medium, is known as a mechanical wave.

Characteristics of a mechanical wave:

1. For the propagation of a mechanical wave, a material medium is necessary. This wave cannot propagate through vacuum.
2. Each particle of the medium forces the adjacent particles to vibrate, but the particle itself is not carried away from its equilibrium position; rather, the wave advances through the medium.
3. The vibrating particles of any material medium have their own mechanical energies (kinetic energy and potential energy). This mechanical energy is transferred from particle to particle due to forced vibration, i.e., a wave in motion transfers mechanical energy through the medium. So, this type of wave is called a mechanical wave.