Ncert Exercises & Solutions

A plane EM wave travelling along z-direction is described by $\vec{E} = E_{0} \sin (kz - ωt) \hat{i} and \vec{B} = B_{0} \sin (kz - ωt) \hat{j} . Show that :$

(i) the average energy density of the wave is given by $U_{av}=\frac14\varepsilon_0E^2_0+\frac14\frac{B^2_0}{\mu_0}$

(ii) the time averaged intensity of the wave is given by $I_{av}=\frac12c\varepsilon_0E^2_0$.