Practice question

**Total internal reflection** occurs when light travels from denser to rarer medium and incidence > C, condition sinC = 1/n for air interface. For glass n=1.52 C≈41°, water n=1.33 C≈48.8°, so at 49° water-air TIR occurs, explaining why ray does not emerge. Critical angle: sin i_c = (n₂/n₁) . Glass ( n₁ = 1.62 ), air ( n₂ = 1 ). sin i_c = (1/1.62) ≈ 0.617 . i_c = sin⁻¹(0.617) ≈ 38.1° . Substituting values gives 38°, which matches expected image position and magnification from mirror/lens formula 1/f = 1/v - 1/u (lens) or 1/f = 1/v + 1/u (mirror), confirming sign conventions and refraction principles.