Calculate angles of refraction using Snell's law
Common refractive indices: Air ≈ 1.00, Water ≈ 1.33, Glass ≈ 1.5
n₁ sin(θ₁) = n₂ sin(θ₂)
Critical angle: θ_c = arcsin(n₂/n₁) when n₁ > n₂
