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Refraction and Reflection


Excerpt from Field Guide to Geometrical Optics

snells_law

Snell's law of refraction:

equation_1

The incident ray, the refracted ray and the surface normal are coplanar.

When propagating through a series of parallel interfaces, the quantity nsinθ is conserved.

law_of_reflection

Law of reflection:

equation_2

The incident ray, the reflected ray and the surface normal are coplanar.

Reflection equals refraction with n2 = –n1.

Total internal reflection TIR occurs when the angle of incidence of a ray propagating from a higher index medium to a lower index medium exceeds the critical angle.

Total_internal_reflection

equation_3

At the critical angle, the angle of refraction θ2 equals 90°.

The reflectance ρ of an interface between n1 and n2 is given by the Fresnel reflection coefficients. At normal incidence with no absorption,

equation_4

Citation:

J. E. Greivenkamp, Field Guide to Geometrical Optics, SPIE Press, Bellingham, WA (2004).



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