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

Options

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

Answer

A

Explanation

`E_(rms) = 720`
The average total energy density
`= (1)/(2) epsilon_(0) E_(0)^(2)= (1)/(2) epsilon_(0) [sqrt2E_(rms))] ^(2) = epsilon _(0) E_(rms)^(2)`
`= 8.85 xx 10^(-12) xx (720)^(2) = 4.38 xx 10^(-6)J//m^(3)`