The Snell’s Law calculator uses Snell’s equation: n₁sin(θ₁) = n₂sin(θ₂), where n₁ is the refractive index of the first medium, n₂ is the refractive index of the second medium, θ₁ is the incident angle, and θ₂ is the refracted angle. To compute any of the four variables, input three known values, and the calculator will automatically find the missing value for you. Please use dots (.) instead of commas for partial numbers.