The energy density associated with electric field \( \vec{E} \) and magnetic field \( \vec{B} \) of an electromagnetic wave in free space is given by ( \( \varepsilon_{0} \) – permittivity of free space, \( \mu_{0} \) – permeability of free space)
\( U_{E} = \dfrac{\varepsilon_{0} E^{2}}{2} , \; U_{B} = \dfrac{\mu_{0} B^{2}}{2} \)
\( U_{E} = \dfrac{\varepsilon_{0} E^{2}}{2} , \; U_{B} = \dfrac{B^{2}}{2\mu_{0}} \)
\( U_{E} = \dfrac{E^{2}}{2\varepsilon_{0}} , \; U_{B} = \dfrac{\mu_{0} B^{2}}{2} \)
\( U_{E} = \dfrac{E^{2}}{2\varepsilon_{0}} , \; U_{B} = \dfrac{B^{2}}{2\mu_{0}} \)
