Light is an electromagnetic wave that consists in an electric field (E) that varies over time while generating a magnetic field (B) and vice versa, since the variable electric fields generate magnetic fields (Ampere's law) and magnetic fields generate electric fields (Faraday's law). Thus, the wave is indefinitely self-propagating through space with electric and magnetic fields generated continuously. These electromagnetic waves are sinusoidal, with electric and magnetic fields perpendicular to each other and about the direction of propagation. See figure on the right.
To describe an electromagnetic wave we can use the usual parameters of any waves:
Amplitude (A): The maximum length from the position of equilibrium that reaches the wave displacement.
Period (T): The time necessary for the passage of two successive maxima or minima for a fixed point in space.
Frequency (f): Number of field oscillations per unit of time. Is a quantity inverse of the period.
Wavelength (λ): The linear distance between two equivalent points of successive waves.
Velocity (V): The distance traveled by the wave in one time unit. In the case of the speed of propagation of light in vacuum, is represented by the letter c.
Representation of an electromagnetic wave in an instant.