Question

The speed of light in a medium M is $$2.5 \times 10^{8} \mathrm{~ms}^{-1}$$. If the speed of light in air is $$3 \times 10^{8} \mathrm{~ms}^{-1}$$, the refractive index of the medium is:

Options

• 1.20

• 1.15

• 1.25

• 1.18

Answer 1

1.20

Explanation:

The refractive index is the ratio of the speed in air to the speed in the medium:

$$\mu=\frac{3 \times 10^{8}}{2.5 \times 10^{8}}=1.20$$