Refraction and TIR Questions

Q1. Which of the following is correct when total internal reflection occurs?

A	The angle of incidence is less than the critical angle.
B	The light meets an optically less dense medium.
C	The light enters a medium with a higher refractive index.
D	The angles that the incident and refracted rays make with the normal are the same.

Q2. Calculate the speed of light in glass of refractive index 1.42

n = c/c_s

c_s = c/n

c_s = 3.00 × 10⁸/1.42

c_s = 3.00 × 10⁸

c_s = 2.11 × 10⁸ m s^–1

Choice B

Q3. The diagram below shows a ray of light travelling in air and incident on a glass block of refractive index 1.5

What is the angle of refraction in the glass?

n₁ sin θ₁ = n₂ sin θ₂

n_air sin θ_air = n_glass sin θ_glass

θ_air = 90^o - 35^o = 55^o

1 x sin 55^o = 1.5 x sin r

sin r = sin 55^o/1.50

sin r = 0.546

r = 33.1^o

Choice C