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