Question

If the critical angle for total internal reflection from a medium to a vacuum is 45°, then the velocity of light in the medium is ______.

Options

• 3 × 10⁸ m/s

• 1.5 × 10⁸ m/s

• `3/sqrt2 xx 10^8  m//s`

• `sqrt2 xx 10^8  m//s`

Answer 1

If the critical angle for total internal reflection from a medium to a vacuum is 45°, then the velocity of light in the medium is `bbunderline(3/sqrt2 xx 10^8  m//s)`.

Explanation:

sin C = `1/n`

sin 45° = `1/n`

`1/sqrt2 = 1/n`

n = `sqrt2`

Then, velocity of light in medium

v = `c/n`

= `3/sqrt2 xx 10^8  m//s`