question_answer

When a plane electromagnetic wave travels in vacuum, the average electric energy density is given by (here \[{{E}_{0}}\]is the amplitude of the electric field of the wave)

A) \[\frac{1}{4}{{\varepsilon }_{0}}E_{0}^{2}\]                  

B) \[\frac{1}{2}{{\varepsilon }_{0}}E_{0}^{2}\]      

C)      \[2{{\varepsilon }_{0}}E_{0}^{2}\]           

D)      \[4{{\varepsilon }_{0}}E_{0}^{2}\]