The Poynting vector is not an electromagnetic wave itself, but rather a mathematical quantity that describes the flow of energy associated with an electromagnetic wave.
The Poynting vector, named after the physicist John Henry Poynting, is defined as the cross product of the electric field vector (E) and the magnetic field vector (B). Mathematically, it is expressed as:
S = E x B
The direction of the Poynting vector represents the direction of energy flow, while its magnitude represents the intensity or power per unit area carried by the electromagnetic wave.
In an electromagnetic wave, the Poynting vector describes the propagation of energy through space as the wave travels. It indicates the direction in which energy is being transported by the wave. The magnitude of the Poynting vector gives the intensity of energy flow, which corresponds to the power carried by the wave per unit area.
So, while the Poynting vector is not an electromagnetic wave itself, it provides a useful mathematical representation of the energy associated with electromagnetic waves and helps to understand the energy transfer properties of electromagnetic radiation.