Q.

In a medium the speed of light wave decreases to 0.2 times to its speed in free space. The ratio of relative permittivity to the refractive index of the medium is x:1. The value of x is _______. (Given speed of light in free space =3×108 ms-1 and for the given medium μr=1)            [2023]


Ans.

(5)

v=Cμ  μ=Cv=C0.2C=5

μ=εrμr  εr=μ2μr

εrμ=μμr=5