What is Wave – Types of Waves

Wave:

Definition: A wave is a disturbance of some kind that propagates through a medium from one place to another"

                                                                             (OR)

"Wave is a mechanism, which is used to transfer energy and momentum from one place to another without transporting matter"

Examples:

i.               A large amount of heat energy from the sun reaches us in the form of waves.

ii.            Sound (energy) reaches our ears by means of waves in the air around us.

Explanation:

In the above definition of wave, the word 'medium' means a substance or material which carries the wave. Some waves required medium for their propagation, while some waves do not required medium for their propagation.

The nature of the wave may be different, but the mechanism by which it transports energy is the same.

Types of Waves:

Waves are of three types, which are discussed below.

1)      Mechanical Waves:

Definition: "The waves which required a material medium for their propagation are called mechanical waves".                              (OR)

"The waves which propagate by the oscillation of material particles are called mechanical waves".

These waves propagate by the oscillation of material particles.

           Examples:

Water waves, string waves, sound waves etc.

Types of Mechanical Waves

        There are two types of mechanical waves:

        Longitudinal waves:

            In this type of wave, the movement of the particle are parallel to the motion of the energy i.e. the displacement of the medium is in the same direction to which the wave is moving.

         Example      Sound Waves, Pressure Waves.

            Transverse waves:

             Difinition:       When the movement of the particles is at right angles or perpendicular to the motion of the energy, then this type of wave is known as Transverse wave.

Transverse waves consists of crests and troughs.

Examples:    Light wave

Difference Between Longitudinal and Transverse Waves

Longitudinal Waves	Transverse Waves
In longitudinal waves, the particles of the medium vibrate parallel to the direction of propagation of wave.	In transverse waves, the particles of the medium vibrate perpendicular to the direction of propagation of wave.
Longitudinal waves consists of compression and rarefaction.	Transverse waves consists of crest and trough.
There is a change in the density throughout the medium.	There is no change in the density of the medium.
There is a pressure variation throughout the medium.	There are no pressure variation.
Longitudinal waves are only mechanical waves.	Transverse waves may be mechanical or electromagnetic in nature.
Longitudinal wave cannot be polarized.	Transverse wave can be polarized.
Examples:   Sound waves	Examples:    Light waves

2) Electromagnetic Waves:

Definition:          "The waves which are produced due to the oscillations of electric and magnetic fields and they require no medium for their propagation are called electromagnetic waves".

These waves propagate due to the oscillations of electric and magnetic field.

        Electromagnetic waves are created by a fusion of electric and magnetic fields. The light you see,the colors around you are visible because of electromagnetic wave.

Examples:

Radio waves, light waves, micro waves, x-rays, ultraviolet waves etc.

Difference between Mechanical Wave and Non Mechanical Wave

Mechanical Wave	Non Mechanical Wave
Mechanical waves are waves that need a medium for propagation.	Non-mechanical waves are waves that do not need a medium for propagation.
Sound waves, water waves and seismic waves are some examples of mechanical waves.	The electromagnetic wave is the only non-mechanical wave.
Mechanical waves cannot travel through vacuum.	Non-mechanical waves can travel through vacuum.

3)      Matter Waves:

        Definition: "The waves associated with material particles in motion are called matter waves”.

         All matter exhibits wave-like behavior. The dual nature of matter; its ability to exist both as a particle and a wave was first brought to light by the founders of the field of Quantum Physics.

        For example, a beam of electrons can be diffracted just like any other beam of electromagnetic radiation or water wave. This property of matter was brought forward by Louis de Broglie's Hypothesis 

    The de Broglie wavelength is the wavelength, λ, associated with a massive particle (i.e., a particle with mass m, as opposed to a massless particle) and is related to its momentum, p, through the Plank constant, h as:

                λ = h / p    =  h / mv        ∵       p = mv

Examples:          

      Wave associated with the motion of electron.

Difference between Stationary waves and Progressive waves

Progressive Waves	Stationary waves
Those waves which are produced in a medium due to some kind of disturbance, as a result of which energy is transmitted from one place to another place, are called as progressive waves.	When two wave trains of the same frequency and amplitude travel in a medium along the same line in opposite directions are superimposed each other and as a result stationary waves are formed.
The amplitude of each particle is the same but the phase changes continuously.	The amplitude of the different particles is different, ranging from zero at the node to maximum at the anti-node. All the particles in a given segment vibrates in phase but in opposite phase relative to the particles in the adjacent segment.
All the particles attain the same maximum velocity when they pass through their mean position.	Al  the particles attain their own maximum velocity at the same time when they pass through their mean position.
No particle is permanently at rest. Different particles attain the state of momentary rest at different instants.	The particles at the nodes are permanently at rest but other particles attain their position of momentary rest simultaneously.
All the particles of the medium undergo similar variation of density one after the other. At every point there will be a density variation.	The variation of density is deferent at different points being maximum at the nodes and zero at the anti-nodes.
There is a flow of energy across every plane in the direction of propagation.	Energy is not transported across any plane.

Necessary Conditions For Wave Motion:

Since the propagation of waves occurs by the interaction of the particle of the medium, so the following conditions are necessary for the propagation of wave.

1.             The medium must be elastic.
2.            The particle of the medium should not be independent of each other so that to exert force on each other.

Transverse and longitudinal waves can be set up in solid. In fluids however transverse wave die out very quickly and usually cannot produce.