The ratio of average electric energy density and total average energy density of electromagnetic wave is:

Question

TestHub · Accepted Answer

Average electric energy density is stated as $u_{E} = \frac{1}{2} ε_{0} E^{2}$

Total average energy density $U = \frac{1}{2} ε_{0} E^{2} + \frac{1}{2 μ_{0}} B^{2}$

$= \frac{1}{2} ε_{0} E^{2} + \frac{1}{2 μ_{0}} \frac{E^{2}}{c^{2}}$ (As $B = \frac{E}{c}$ )

$= \frac{1}{2} ε_{0} E^{2} + \frac{1}{2 μ_{0}} E^{2} ε_{0} μ_{0} = \frac{1}{2} ε_{0} E^{2} + \frac{1}{2} E^{2} ε_{0} = ε_{0} E^{2}$

Hence, the ratio, $\frac{u_{E}}{U} = \frac{1}{2}$ .

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