Question

The root-mean-square (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. $3.3\times 10^{- 3}Jm^{- 3}$

Answer 1

Answer: (A)

Total average energy $=\epsilon _{0}E_{r m s}^{2}$
$=8.85\times 10^{- 12}\times 720 ^{2}$