Question

The absolute refractive indices of glass and water are 4/3 and 3/2 respectively. If the speed of light in glass is 2 x 10^8 m/s , calculate the speed of light in 1) vacuum 2) water

Answer 1

Actually, ng = 3/2 and nw = 4/3.

Absolute Refractive Index of a medium = Speed of light in vacuum/Speed of light in the medium

Speed of light in glass = 2 x 108 m/s
Speed of Light in Vacuum = (3/2) x 2 x 108 m/s = 3 x 108 m/s

Speed of light in water = (3 x 108 m/s)/(4/3)
                                        = 2.25 x 108 m/s