Practice question

**TIR application** requires n₁>n₂ and θ₁>C. Critical angle formula derived from Snell's law with θ₂=90°, n₁ sinC = n₂ sin90° = n₂, so sinC = n₂/n₁. For glass-air sinC=1/1.52, C≈41°, for water-air 48.6°, determining cutoff for transmission. Focal length: f = 24 cm , u = -16 cm . Mirror equation: (1/v) + (1/-16) = (1/24) ⇒ (1/v) = (1/24) + (1/16) = (2 + 3/48) = (5/48) . v = (48/5) = 9.6 cm (virtual image). Substituting values gives 9.6 cm, 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),