Velocity of an Electromagnetic Wave
An electromagnetic wave is a transverse wave that consists of electric and magnetic field components oscillating perpendicular to each other and to the direction of wave propagation. The velocity of an electromagnetic wave in a medium is a property that depends on the medium in which it is traveling.

Explanation
- The velocity of an electromagnetic wave in a vacuum is constant and is denoted by the symbol 'c', which is approximately equal to 3 x 10^8 m/s. This speed is the fastest speed at which any form of energy can travel in a vacuum.
- When an electromagnetic wave travels through a medium other than a vacuum, such as air, water, or glass, its velocity changes. The speed of light in a medium is typically less than its speed in a vacuum due to interactions with the atoms and molecules of the medium.
- The velocity of an electromagnetic wave in a medium is determined by the properties of the medium, such as its refractive index. The refractive index of a medium is a measure of how much the speed of light is reduced when it passes through the medium.
- The relationship between the velocity of light in a medium (v), the speed of light in a vacuum (c), and the refractive index of the medium (n) is given by the equation v = c/n.
- Therefore, the velocity of an electromagnetic wave, which is a fundamental property of the wave, depends on the medium through which it is traveling.
In conclusion, the velocity of an electromagnetic wave is a property that depends on the medium in which it is traveling, making it a key factor in understanding the behavior of light and other electromagnetic waves in different substances.