What Snell’s Law describes
Snell’s Law describes how light bends as it passes from one transparent medium into another with a different refractive index. It states that n₁·sin(θ₁) = n₂·sin(θ₂), where n₁ and n₂ are the refractive indices of the two media and θ₁, θ₂ are the angles of incidence and refraction from the normal.
How this calculator works
Enter the refractive indices of both media and the angle of incidence. The calculator rearranges Snell’s Law to solve for sin(θ₂), then takes the inverse sine to find the angle of refraction in degrees.
When light travels from a denser to a less dense medium at a steep enough angle, total internal reflection can occur and no refracted ray exists; the calculator flags this case instead of showing an invalid result. For general educational purposes.
Last reviewed August 2026