In an electromagnetic wave, the amplitude of electric field is 1 V/m. the frequency of wave is 5× 1014Hz. The wave is propagating along z-axis. The average energy density of electric field, in Joulem3, will be
2.2× 10−12
Average energy density of electric field is given by
ue=12ϵ0E2=12ϵ0(E0√2)2=14ϵ0E20
=14× 8.85× 10−12(1)2=2.2× 10−12J/m3.