### Wave

Wave- A wave can be described as a disturbance that travels through a medium from one location to another location without the transport of matter.

Types of Waves
Waves can be said of two types – 1. Mechanical Wave and 2. Non – Mechanical Wave

Mechanical Wave- These are waves which require some material medium (solid or liquid or gas) to travel. These waves also called elastic waves.

Again Mechanical waves can be said of two types-

Longitudinal Waves- When the particles of medium vibrate in the direction of propagation of wave, the wave is called longitudinal wave. Waves on spring and sound waves in air are some of the examples of longitudinal waves.

Transverse Waves- If the particles of the medium vibrate perpendicularly to the direction of propagation of wave, the wave is called transverse wave.

Some of the examples of transverse waves are- water wave, waves on string under tension etc.

Non-mechanical Waves or Electromagnetic Waves- The waves which do not require any medium to travel means which can propagate even through vacuum are called non mechanical waves. Examples of electromagnetic waves are – light waves and heat waves. All the electromagnetic waves are non mechanical.

Properties of Electromagnetic Waves
•    They are neutral.
•    They propagate as transverse wave.
•    They propagate with the velocity of light.
•    They contain energy and momentum.
•    The concept of electromagnetic waves was given by Maxwell.

Some Important Electromagnetic Waves

 Electromagnetic Wave Discoverer Wavelength Range in Meters Frequency Range ¡- Rays Henry Becqueral 10-14 to 10-10 1020 to 1018 X-Rays W. Rontgen 10-10 to 10-8 1018 to 1016 Ultra-violet Rays Ritter 10-8 to 10-7 1016 to 1014 Visible radiation Newton 3.9x10-7 to 7.8x10-7 1014 to 1012 Infrared Rays Hershel 7.8x10-7 to 7.8x10-3 1012 to 1010 Short Radio Waves or Hertz Hertzian Waves Heinrich 10-3 to 1 1010 to 108 Long Radio Waves Marcony 1 to 104 108 to 106

The electromagnetic waves in the wavelength range 10-3 m to 10-2 m are called microwaves.

Phase of Vibration- The phase of vibration of a vibrating particle at any instant is the physical quantity which defines the position as well as direction of the motion of the particle at that instant with respect to the equilibrium or mean position.

Amplitude – Amplitude is defined as the maximum displacement of the vibrating particle on either side from the equilibrium position.

Wavelength – Wavelength is the distance between any two nearest particles of the medium, vibrating in the same phase. It is denoted by Greek symbol ƛ.

In transverse waves, the distance between two consecutive crests and troughs and in longitudinal wave, distance between two consecutive compressions or rarefaction is equal to wavelength.

Relation between wavelength, frequency and velocity of wave
Velocity of Wave = Frequency x Wavelength or 𝝂=nƛ