Question

If the critical angle for total internal reflection from a medium to vacuum is 30°, the velocity of light in the medium is ______.

Options

• 3 × 10⁸ m/s

• 1.5 × 10⁸ m/s

• 6 × 10⁸ m/s

• `sqrt3` × 10⁸ m/s

Answer 1

If the critical angle for total internal reflection from a medium to vacuum is 30°, the velocity of light in the medium is 1.5 × 10⁸ m/s.

Explanation:

sin i_c = `1/(""_"r"mu_"d") = mu_"r"/mu_"d" = "v"_"d"/"v"_"r"`

sin 30° = `"V"_"d"/(3xx10^8)`

⇒ v_d = 1.5 × 10⁸ m/s