Electromagnetic wave equation

Summary

The electromagnetic wave equation is the vector wave equation satisfied by the electric field and the magnetic field in a region without charges and currents. It follows from Maxwell's equations and shows that electromagnetic disturbances travel at the speed $c = 1/\sqrt{\varepsilon_0 \mu_0}$ in vacuum. Maxwell's identification of this speed with the measured speed of light showed that light is an electromagnetic wave. In a linear homogeneous medium the same equation holds with the slower speed $1/\sqrt{\varepsilon \mu}$.