Optics

The colors of a soap film

Aseem Raj Baranwal derives the colors of a draining soap film from first principles: the reflected spectrum of a thin film is a single cosine in 1/λ, so its color is a fixed white minus the cosine transform of the CIE color-matching functions at the extra optical path 2nd, and the computed colors match the table of thicknesses Newton compiled in Opticks.

Blog post · Physics · Optics · Mathematics