Find the refraction angle from n₁ sin θ₁ = n₂ sin θ₂, or TIR if there is no transmitted ray.
| θ₂ (°) | – |
Use this calculator for Snell’s law at a flat interface: n₁ sin θ₁ = n₂ sin θ₂. Angles are from the normal, in degrees.
Air is n ≈ 1, water ≈ 1.33, glass ≈ 1.5. Going into a slower medium (larger n) bends the ray toward the normal. If n1 > n2 and θ₁ is too large, sin θ₂ would exceed 1: total internal reflection, labelled TIR. This is a geometric ray, not a wave-optics fringe.
n₁: Refractive index of the first medium.
n₂: Refractive index of the second medium.
θ₁ (°): Angle of incidence from the normal, in degrees.
θ₂ (°): Angle of refraction, or TIR if there is no transmitted ray.
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