Question

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 × 10⁸ ms⁻¹. 

Answer 1

We know: 

Refractive index = Speed of light in air/Speed of light in diamond

Let X be the speed of light in diamond. Now, we have:
2.42 = 3.0 × 10⁸ ms^-1 / X
X = 1.24 × 10⁸ ms^-1