Snell's Law

Refraction angle and critical angle with a ray diagram

1 · sin(θ₁) = 1.5 · sin(θ₂)
Refraction angle (θ₂)
19.47°
Critical angle (θc)
None (n₁ ≤ n₂)

Light bends toward the normal when entering a denser medium (n₂ > n₁) and away from it when entering a rarer one. Snell's law relates the angles: n₁·sin(θ₁) = n₂·sin(θ₂).

Snell's LawAn incident ray meets the boundary at 30° from the normal. With n₁ = 1 and n₂ = 1.5, the refracted ray leaves at 19.5° in medium 2.30°19.5°Medium 1 (n₁)Medium 2 (n₂)