A plane electromagnetic wave in a non-magnetic medium is E=20 cos(2×10¹⁰t-200x) V/m. Find the dielectric constant. Take μᵣ=1.
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Question

A plane electromagnetic wave in a non-magnetic medium is E=20 cos(2×10¹⁰t−200x) V/m. Find the dielectric constant. Take μᵣ=1.

G1 Physics · Accepted Answer

From E=20cos(ωt−kx), v=ω/k=(2×10¹⁰)/200=1×10⁸ m/s. For μᵣ=1, v=c/√εᵣ, so εᵣ=(c/v)²=(3×10⁸/10⁸)²=9. Option A.