The interference of polarised light

This article brings out a remarkable contribution to the understanding of light, made by S (for Sivaramakrishnan) Pancharatnam, when he was a doctoral student working on the optics of crystals with C V Raman at the Raman Research Institute (RRI) in Bangalore in the 1950s. We will first illustrate this contribution by means of specific examples, which already calls for considerable background, and then go on to place the work in a wider context.