Snell's Law: How light bends crossing between media; critical angle & TIR. This free calculator solves for Refraction angle, critical angle and shows every step.
Light bends when it crosses between media of different optical density because its speed changes. When light travels from a denser to a rarer medium beyond the critical angle, it reflects entirely — total internal reflection — the principle behind fibre optics.
Air (n₁ = 1.00) into glass (n₂ = 1.50) at θ₁ = 30°. sinθ₂ = (1·sin30°)/1.50 = 0.333 → θ₂ = 19.5° (bends toward the normal).
Lens and camera design, fibre-optic communications, prisms and spectroscopy, eyeglasses, mirages.
Snell's Law uses the formula n₁·sinθ₁ = n₂·sinθ₂. How light bends crossing between media; critical angle & TIR.
Choose which variable to solve for, enter the values you know (in any supported unit), and the calculator substitutes them into n₁·sinθ₁ = n₂·sinθ₂ and shows every step of the working. It can solve for Refraction angle, critical angle.
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