Waves & Optics
Snell's Law Calculator
Calculate refraction angle, find the critical angle for total internal reflection, and look up refractive indices for common materials. Live ray diagram updates instantly.
n₁sinθ₁ = n₂sinθ₂
Quick examples
Ray diagram
Enter angle of incidence (0–89°) to calculate.
Snell's Law — key equations
Snell's Law
n₁sinθ₁ = n₂sinθ₂
Refraction angle
θ₂ = arcsin(n₁sinθ₁/n₂)
Critical angle
θ_c = arcsin(n₂/n₁)
Refractive index
n = c/v (c = speed of light)
Relative index
n₁₂ = n₁/n₂
TIR condition
θ > θ_c when n₁ > n₂