The rms value of the electric field of the light from the sun is `720 N//C` The total energy density of the electromagnetic wave is

Options

A. `6.37 xx 10^(-9) J//m^(3)`
B. `81.35 xx 10^(-12) J//m^(3)`
C. `3.3 xx 10^(-3) J//m^(3)`
D. `4.58 xx 10^(-6) J//m^(3)`

Answer

D

Explanation

`U_(av) = (1)/(2)in_(0) E_(0)^(2) = (1)/(2)in_(0)(sqrt(2)E_(rms))^(2) = in_(0) E_(rms)^(2)`
`= 8.85 xx 10^(-12) xx (720)^(2) = 4.58 xx 10^(-6) J//m^(2)`