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. `4.58xx10^(-6)J//m^(3)`
B. `6.37xx10^(-9)J//m^(3)`
C. `81.35xx10^(-12)J//m^(3)`
D. `3.3xx10^(-3)J//m^(3)`

Answer

A

Explanation

`E_("rms")=720`
The average total energy density
`=(1)/(2)in_(0)E_(0)^(2)=(1)/(2)in_(0)[sqrt2E_("rms")]^(2)=in_(0)E_("rms")^(2)`
`=8.85xx10^(-12)xx(720)^(2)=4.58xx10^(-6)J//m^(3)`