Solution:

Given

According to the question, speed of light in air is

c = 3 × 10⁸ m / s

And the refractive index of glass is

μ = 1.5

We have to calculate the speed of light in glass, v

Using the expression below,

c / v = μ

Upon re-arranging we have => v = c / μ

v = 3 × 10⁸ m / s / 1.5

Therefore, v = 2 × 10⁸ m / s