Q. The rms value of the electric field of the light coming from the sun is 720 NC$^{-1}$. The average total energy density of the Electromagnetic Wave is
A) $4.58\ \times \ 10^{- 6}\ {Jm}^{- 3}$
B) $6.37\ \times \ 10^{- 9}\ Jm^{- 3}$
C) $81.35\ \times 10^{- 12}\ {Jm}^{- 3}$
D) $3.3\ \times 10^{- 3}{Jm}^{- 3}$
Explanation
(a) Total average energy $= \ \varepsilon_{0}E_{rms}^{2}$
$= \ 8.85\ \times \ 10^{- 12}\ \times \ (720)^{2}$
$= \ 4.58\ \times \ 10^{- 6}\ {Jm}^{- 3}$
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.