All the light from the Newton’s Prism: Effects of the multiple internal reflections

Abstract

White-light dispersion experiments performed by Newton with prisms remain among the most beautiful in optics and are frequently replicated in schools and universities. But there is an aspect that is little considered, namely that the light initially refracted within the equilateral prism, in addition to being further refracted and giving out the well-known spectrally dispersed bundle, is also internally reflected an indefinite number of times and, in correspondence with each reflection, produces an external refractive bundle that can be white or dispersed depending on the parity of the number of reflections previously undergone. In this paper, I analyze, both theoretically and experimentally, the properties of the main bundles coming out of the faces of the equilateral prism, when it is illuminated by p- or s-polarized white light, or by a laser beam.