When an electromagnetic wave at normal incidence on a perfectly conducting surface is reflected, the electric field of the reflected wave at the reflecting surface is equal and opposite to the electric field of the incident wave at the reflecting surface.

(a) explain why this assertion is valid.
(b) show that the superposition of incident and reflected waves results in a standing wave.
(c) are the magnetic fields of the incident waves and reflected waves at the reflecting surface equal and opposite as well