Question

The rms value of the electric field of the light coming from sun is 720 N $C^{-1}$. The average total energy density of the electromagnetic wave is

• A. $3.3{10}^{-3}J{m}^{-3}$
• B. $4.58{10}^{-6}J{m}^{-3}$
• C. $6.37{10}^{-9}J{m}^{-3}$
• D. $81.35{10}^{-12}J{m}^{-3}$

Answer 1

The correct option is B $4.58{10}^{-6}J{m}^{-3}$

Given: The RMS value of the electric field of light is $720N/C$.

Energy density of electromagnetic wave is given by:

$E={ϵ}_0{E}_{rms}^2$

$=8.85\times {10}^{-12}\times (720{)}^2$

$E\approx 4.58\times {10}^{-6}J/m^3$

Option $\left(B\right)$ is corret.