Different Types of Waves

The waves can be of different types. These may be mechanical or electromagneticMechanical wave is a term used for those waves that require a medium for travelling. Its speed is dependent on the properties of the medium such as inertial and elastic properties.

In other words the speed of the wave will depend on how easy or difficult it is to displace the particles of the medium (that is to say on their inertia) and on how those particles regain their original positions which is the elasticity.

An electromagnetic wave results from acceleration of charge. It doesn't require a medium to travel. It can travel through vacuum such as light waves which travel from stars through empty space to reach us. The electromagnetic wave has electric and magnetic fields associated with it. The two fields, electric and magnetic, are perpendicular to each other and also to the direction of propagation.

The Sound wave is a mechanical wave but light waves, infra red rays, X-rays, microwaves, radio waves are electromagnetic. Gamma rays are also em waves and result from radioactive decay of nuclei of atoms. Compared to sound waves, the em are much more energetic. They travel at the velocity of light that is about 3 lac km per second in vacuum. In comparison, the sound waves travel very slowly. In air, it travels at 330 m s-1. Sound moves faster in the solids than in gases or liquids.

Such difference in the velocities of light and sound means if there is an event in the sky, which produces light and sound both, we shall see the light almost instantly but it will be a while before we hear it. When there is a lightening in the sky, we see the light before we hear the sound.

Mechanical wave can be either transverse or longitudinal while the electromagnetic wave is only transverse. The transverse wave is one in which the motion of wave and of the particles are perpendicular to each other. In a longitudinal wave, the motions are in the same direction. The sound wave can be of two types: Transverse and longitudinal.

In a transverse wave, the particles of the medium move perpendicular to the direction of wave movement.

In a longitudinal wave, the displacement of the particles and propagation of the wave are in the same direction. Just like the distance between two successive crests or troughs is a measure of wavelength for transverse waves, the distance between two successive compressions or rarefactions is termed wavelength of the longitudinal wave.

While transverse waves form only in fluids (air and liquid), the longitudinal waves can form in all the three media - solid, liquid and gas.