The electric field of an electromagnetic wave has amplitude E₀ = 20 N C⁻¹. The energy contained in a volume 5 × 10⁻⁴ m³ is: (ε₀ = 8.85 × 10⁻¹² C² N⁻¹ m⁻²)
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The electric field of an electromagnetic wave has amplitude E₀ = 20 N C⁻¹. The energy contained in a volume 5 × 10⁻⁴ m³ is: (ε₀ = 8.85 × 10⁻¹² C² N⁻¹ m⁻²)

G1 Physics · Accepted Answer

The average total energy density of an electromagnetic wave is ⟨u⟩ = (1/2)ε₀E₀². ⟨u⟩ = (1/2)(8.85×10⁻¹²)(20)² = 1.77×10⁻⁹ J m⁻³. Energy = ⟨u⟩V = (1.77×10⁻⁹)(5×10⁻⁴) = 8.85×10⁻¹³ J.