Practice question

**Refraction at plane surface** changes direction due to speed change v = c/n, n = c/v. For water n=1.33 to air, n₁>n₂, ray bends away, if θ₁ > C, sinθ₂>1 impossible, TIR occurs. Snell's law quantitative prediction of θ₂ from θ₁ and indices. Snell’s law: n₁ sin i = n₂ sin r . Air ( n₁ = 1 ), water ( n₂ = 1.33 ), i = 35° . 1 × sin 35° = 1.33 × sin r . sin 35° ≈ 0.574 ⇒ 0.574 = 1.33 sin r ⇒ sin r = (0.574/1.33) ≈ 0.432 . r = sin⁻¹(0.432) ≈ 25.6° . Substituting values