Question

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 $=3 \times 10^8 m s ^{-1}$ and for the given medium $\mu =1$)

Answer 1

The correct answer is 5.
V=μC​⇒μ=VC​=0.2CC​
μ=5
μ=ϵr​μr​​
⇒ϵr​=μr​μ2​
∴μϵr​​=μr​μ​=5