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

Answer

B

Explanation

The average density of electromagnetic field is
`=epsi_0 E_(rms )^(2)`
`= 8.85 xx 10^(-12) xx ( 720 )^2 = 4.59 xx 10^(-6) J//m ^3`