An electromagnetic wave of frequency 1x1014 hertz is propagating along z - axis. The amplitude of electric field is 4 V/m.          If \epsilon _{0} = 8.8 x 10-12 C2/N-m2, then average energy density of electric field will be :

A.

 35.2 x 10-10 J/m3

B.

 35.2 x 10-11 J/m3

C.

 35.2 x 10-12 J/m3

D.

 35.2 x 10-13 J/m3

Answers (1)

Average Energy density of Electromagnetic wave is given by

\mu_{e}=\frac{1}{2}\varepsilon _{0}E^{2}

E=\frac{E_{0}}{\sqrt{2}}

\mu_{e}=\frac{1}{2}\varepsilon _{0}\left (\frac{E_{0}}{\sqrt{2}} \right )^{2}

\mu_{e}=\frac{1}{4}\varepsilon _{0}E_{0}^{2}

\mu_{e}=\frac{1}{4}\times 8.8\times 10^{-12}\times 4^{2}\ J/m^{3}

\mu_{e}=35.2\times 10^{-12} \ J/m^{3}

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