Which is the correct expression of velocity of light?

The velocity of electromagnetic waves in free space is given by

$c=\frac{1}{\sqrt{\mu_0 \varepsilon_0}}=\frac{E_0}{B_0}=3 \times 10^8 ms^{-1}$

Moreover, velocity of light in a medium with refractive index µ is, v = $\frac{c}{µ}$