The velocity of light in a vacuum is $....$

An incident ray falls normally on a glass slab. What is the angle of refraction (in $°$)?

How is the refractive index of a medium related to the speed of light? Obtain an expression for the refractive index of a medium with respect to another in terms of the speed of light in these two media.

As the velocity of light increases,the refractive index of the medium decreases. Light enters from air to water having a refractive index of $4/3$. Find the speed of light in water. The speed of light in vacuum is $3 \times 10^{8} \text{ m s}^{-1}$.

Light enters from air into diamond,which has a refractive index of $2.42$. Calculate the speed of light in diamond. The speed of light in air is $3.0 \times 10^{8} \text{ m s}^{-1}$.

What happens when a light ray incident normally on the surface of a glass slab enters from air into the glass?