What is the time taken by light to travel through a glass slab of thickness ‘d’ and refractive index `mu` ?

If the velocity of light in vacuum is 3xx10^(8)ms^(-1) , the time taken (in nanosecond) to travel through a glass plate of thickness 10 cm and refractive index 1.5 is

Light travels through a glass plate of thickness t and having refractive index mu . If c be the velocity of light in vacuum, time taken by the light to travel through this thickness of glass is

A ray of lilght is incident at a small angle theta on a rectangular glass slab of thickness t. IF the refractive index of glass is mu show that the perpendicular distance between the emergent ray from the slab and the incident ray is theta t (mu-1)//mu