# A plane electromagnetic wave, has frequency of 2.0 × 10^10 Hz and its energy density is 1.02 × 10^–8 J/m^3 in vacuum.

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A plane electromagnetic wave, has frequency of 2.0 × 1010 Hz and its energy density is 1.02 × 10–8 J/m3 in vacuum. The amplitude of the magnetic field of the wave is close to (${1\over4\pi\varepsilon_0}=9\times10^9{Nm^2\over C^2}$ and speed of light = 3 × 108 ms–1) :

(1) 160 nT

(2) 180 nT

(3) 190 nT

(4) 150 nT

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Electromagnetic waves

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verified

Ans : (1) 160 nT

Explanation:

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How did you knw to use this formula ?
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there is only one formula magnetic energy density