A linearly polarized electromagnetic wave given as
Question:

A linearly polarized electromagnetic wave given as $E=E_{0} \hat{i} \cos (k z-\omega t) \quad$ is incident normally on a perfectly reflecting infinite wall at $\mathrm{z}=\mathrm{a}$

Assuming that the material of the wall is optically inactive, the reflected wave will be given as

(a) $E_{r}=-E_{0} \hat{i} \cos (k z-\omega t)$

(b) $E_{r}=E_{0} \hat{i} \cos (k z+\omega t)$

(c) $E_{r}=-E_{0} \hat{i} \cos (k z+\omega t)$

(d) $E_{r}=E_{0} \hat{i} \sin (k z-\omega t)$

Solution:

(b)

$E_{r}=E_{0} \hat{i} \cos (k z+\omega t)$