Question

A glass medium has a refractive index of \[n = 1.5\]. The speed of light in this glass is:

Options

• \[2 \times 10^8 \ \text{m/s}\]

• \[1.5 \times 10^8 \ \text{m/s}\]

• \[4.5 \times 10^8 \ \text{m/s}\]

• \[3 \times 10^8 \ \text{m/s}\]

Answer 1

Using \[v = \frac{c}{n} = \frac{3 \times 10^8}{1.5} = 2 \times 10^8 \ \text{m/s}\]. Light travels slower in glass than in vacuum because the refractive index is greater than 1.