JEE Main 2026 Jan 23 Shift 2, Physics Q18: Electromagnetic Waves

JEE Main2026Jan 23, Shift 2Physics

The ratio of speeds of electromagnetic waves in vacuum and in a medium, having dielectric constant $k = 3$ and permeability of $μ = 2 μ_{0}$ , is

( $μ_{0} =$ permeability of vacuum)

Solution

Refractive index $n = \frac{c}{v} = ε_{r} μ_{r}$ .

With $ε_{r} = 3$ and $μ_{r} = 2$ : $n = 6$ .

$∴ \frac{c}{v} = 6$ , giving the ratio $6 : 1$ .

Concept behind this question

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