Question Detail
Question
The diagram shows a ray of monochromatic light passing through a semi-circular glass block.
What is the refractive index of the glass?
What is the refractive index of the glass?
Correct Answer
Option C is the correct answer.
Detailed Explanation
From the diagram, the ray hits the flat surface from inside the glass at an angle of incidence of 50 degrees to the normal. It then emerges into the air parallel to the surface, meaning the angle of refraction in air is 90 degrees. This implies that 50 degrees is the critical angle (θ_c) for the glass-air interface.Using Snell's Law at the critical angle: n_glass * sin(θ_c) = n_air * sin(90°).Given n_air = 1 (for air) and sin(90°) = 1.n_glass * sin(50°) = 1.n_glass = 1 / sin(50°).sin(50°) ≈ 0.766.n_glass = 1 / 0.766 ≈ 1.305.The closest option is 1.31.
Hint
Recall Snell's Law and the definition of the critical angle when light travels from a denser to a rarer medium.