Which of the following has zero average value in a plane electromagnetic wave?
(A) Electric field
(B) Magnetic field
(C) Electric energy
(D) Magnetic energy
Choose the correct answer from the options given below.
Answer & explanation
Correct answer: option 4
The correct answer is Option (4) → (A) and (B) only
In a plane electromagnetic wave:
→ The electric field (E) and magnetic field (B) are sinusoidal functions of time.
→ Their instantaneous values vary periodically and average to zero over a complete cycle.
→ The electric energy and magnetic energy are proportional to $E^2$ and $B^2$, respectively, so they are always positive and have nonzero average values.
∴ Correct options:(A) Electric field and (B) Magnetic field