How does the refractive index of a transparent medium affect the speed of light passing through it?

The refraction index, n, of a transparent medium is defined as the ratio of the speed of light in the vacuum to the speed of light in that medium. The formula is
$n=\frac{c}{v}$
from the above formula, we can calculate the speed of light in that medium.it decreases, As $v=\frac{c}{n}$
where,
c=speed of light in vacuum
n=refractive index of medium