# Phase Velocity and Group Velocity of Electromagnetic Waves

The velocity of a wave can be defined in many different ways, because of the presence of many different kinds of waves and different aspects or components of any given wave.

We can define the velocity of a wave in two different ways:
1. Phase velocity
2. Group velocity

# Definition of Phase Velocity

The phase velocity of a wave is the rate at which the phase of the wave propagates in space. This is the speed at which the phase of any one frequency component of the wave travels.

In terms of the cyclical frequency and wavelength, we have, .

 âˆ´

# Definition of Group Velocity

The velocity with which the overall shape of a wave amplitude, known as the modulation or envelope of the wave, propagates through a medium is known as the group velocity of the wave. Group velocity is the velocity with which the energy propagates; hence, it is also known as energy velocity.

 âˆ´