Question 159: EM waves

Question

The $rms$ value of the electric field of the light coming from the Sun is $720$ $N/C.$ The average total energy density of the electromagnetic wave is

Accepted Answer

${E_{rms}} = 720$
The average total energy density
$ = {1 \over 2}{ \in _0}\,E_0^2 = {1 \over 2}{ \in _0}{\left[ {\sqrt 2 {E_{rms}}} ight]^2} = { \in _0}\,E_{rms}^2$
$ = 8.85 	imes {10^{ - 12}} 	imes {\left( {720} ight)^2}$
$ = 4.58 	imes {10^{ - 6}}\,J/{m^3}$

Answer

$4.58 	imes {10^{ - 6}}\,J/{m^3}$

Answer

$6.37 	imes {10^{ - 9}}\,J/{m^3}$

Answer

$81.35 	imes {10^{ - 12}}\,J/{m^3}$

Answer

$3.3 	imes {10^{ - 3}}\,J/{m^3}$

EM waves

The rms value of the electric field of the light coming from the Sun is 720 N/C. The average total energy density of the electromagnetic wave is

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