Q. A ray of light travelling in a transparent medium of refractive index μ, falls on a surface separating the medium from air at an angle of incidence of 45º. For which of the following value of μ the ray can undergo total internal reflection?
A) μ = 1.25
B) μ = 1.33
C) μ = 1.40
D) μ = 1.50
Explanation
[Solution from source] TIR needs the incidence angle to exceed the critical angle: sin 45° > 1/μ, so μ > √2 ≈ 1.414. Only μ = 1.50 exceeds this; 1.40 is just below. Answer (4).
Reviewed by Dr. Abubacker
Physics Educator & NEET/JEE Specialist
Ph.D. in Physics with 19+ years of teaching experience.