Astronomy & optics

Refraction and total internal reflection

Calculate the refracted angle from refractive indices and the angle of incidence, and check for total internal reflection.

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Understand the calculation

n₁ sin(θ₁) = n₂ sin(θ₂); critical angle when n₁ > n₂: θcrit = arcsin(n₂/n₁)

Going from n₁ = 1 to n₂ = 1.5, an angle of incidence of 30° gives a refracted angle of approximately 19.47°.

All angles are measured from the normal to the interface.
Total internal reflection can occur when light travels from a higher-index medium to a lower-index medium.