Question #98948

Sep 19, 2017

There is no general description of equation of energy of an EM wave.

However, in the wave picture of radiation, the Electric and magnetic fields can carry energy (equally distributed among both) and the corresponding energy density can be given as,

$u = \left(\frac{{\epsilon}_{0} {E}^{2}}{2} + {B}^{2} / \left(2 {\mu}_{0}\right)\right)$ where $E$ and $B$ are electric and magnetic field magnitudes.

Thus in a volume $d \tau$, the corresponding electromagnetic energy is $E = u d \tau$

However, in the particle picture of radiation, it is considered to be a stream of fast moving particles called photons. In that case, the energy carried by each photon of frequency $\nu$ is,

$E = h \nu$ where $h$ is Planck's constant.