Snell’s law

n₁ sin θ₁ = n₂ sin θ₂. Angles are degrees from the normal. If n₁/n₂ sin θ₁ > 1, the page reports total internal reflection. Dispersion is ignored.

n₁

Angle of incidence

n₂

Angle of refraction

19.47°

Air into glass (1 → 1.5) at 30° is about 19.5°. The trig page is the sine itself. The lens page is 1/f = 1/u + 1/v.

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