In a plane EM wave, the electric field oscillates sinusoidally at a frequency of 5 × 10¹⁰ Hz and an amplitude of 50 V m⁻¹. The total average energy density of the electromagnetic field of the wave is: [Use ε₀ = 8.85 × 10⁻¹² C² N⁻¹ m⁻²]
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Question

In a plane EM wave, the electric field oscillates sinusoidally at a frequency of 5 × 10¹⁰ Hz and an amplitude of 50 V m⁻¹. The total average energy density of the electromagnetic field of the wave is: [Use ε₀ = 8.85 × 10⁻¹² C² N⁻¹ m⁻²]

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G1 Physics · Accepted Answer

Total average energy density: u = (1/2)ε₀E₀² = (1/2)(8.85 × 10⁻¹²)(50)² = 1.106 × 10⁻⁸ J m⁻³