Surface power density

In physics and engineering, surface power density, or sometimes simply specific power is power per unit area. In physics and engineering, surface power density, or sometimes simply specific power is power per unit area. As an electromagnetic wave travels through space, energy is transferred from the source to other objects (receivers). The rate of this energy transfer depends on the strength of the EM field components. Simply put, the rate of energy transfer per unit area (power density) is the product of the electric field strength (E) times the magnetic field strength (H).