A plane electromagnetic waveEz = 100 cos 6 × 108 t + 4x V/mpropagates in a medium of dielectric constant. The refractive index of the medium is

Comparing the given equation with equation of plane electromagnetic wave, Ez = E0 cos (ωt + kx) we have ω = 6 × 10−8  and  k = 4Velocity of light in mediumv=ωk=6×1084=32×108m/sRefractive index, μ = cv=3 × 108(3/2) × 108=2