According to Maxwell’s equation the velocity of light in any medium is expressed as

$\frac{1}{\sqrt{\mu_0ε_0}}$ $\frac{1}{\sqrt{\mu ε}}$ $\sqrt{\mu ε}$ $\sqrt{\frac{\mu}{ε}}$

$\frac{1}{\sqrt{\mu ε}}$

Velocity of light in a medium, $ v =\frac{c}{\sqrt{\mu_r ε_r}}={\frac{1}{\sqrt{\mu_0 ε_0 \mu_r ε_r}}}=\frac{1}{\sqrt{\mu ε}}$