Q. The electric field of a plane electromagnetic wave varies with time of amplitude 2 Vm$^{-1}$ propagating along $z$-axis. The average energy density of the magnetic field is $\left( in\ {Jm}^{- 3} \right)$
A) $13.29\ \times \ 10^{- 12}$
B) 8.86 $\times \ $10$^{-12}$
C) 17.72 $\times$ 10$^{-12}$
D) 4.43 $\times$ 10$^{-12}$
Explanation
(b) U = $\frac{1}{2}\ \times \ \frac{1}{2}\varepsilon_{0}E^{2} = \frac{1}{2}\ \times \frac{1}{2}\ \times \ 8.85\ \times \ 10^{- 12}\ \times \ {(2)}^{2}$
$= 8.85\ \times \ 10^{- 12}{Jm}^{- 3}$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.