When light propagates through a material medium of relative permittivity $\epsilon_r$ and relative permeability $\mu_r$, the velocity of light, $v$ is given by : ($c$ - velocity of light in vacuum)

A $v=\frac{c}{\sqrt{\epsilon_r\mu_r}}$

B $v=c$

C $v=\sqrt{\frac{\mu_r}{\epsilon_r}}$

D $v=\sqrt{\frac{\epsilon_r}{\mu_r}}$

The answer is A.

Solution

Refractive index of the medium $n = \sqrt{\epsilon_r\mu_r}$ $n = \frac{c}{v} \Rightarrow v = \frac{c}{n}$ $v = \frac{c}{\sqrt{\epsilon_r\mu_r}}$

Concept speed of light in a medium

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