The refractive index of glass is 1.5 and the speed of light in air is 3×108 ms−1. Calculate the speed of glass in water.

Refractive index (n) = 1.5

Speed of light in air = 3x 10⁸ ms^-1

Speed of light in water = ?

The refractive index is given by n= c / v

Substituting the given values in the above equation, we will get

v = c / n

= 3×10⁸ m/s / 1.5

∴ v = 2 ×10⁸ m/s

So, the speed of light in glass would be 2 ×10⁸ m/s.