Far-field image of a laser pointer shone through randomly-undulating bathroom-window glass. Caustics separate regions reached by different numbers of rays. The ray caustics are decorated with ‘diffraction catastrophe’ wave patterns. Illustrated here are the Airy function (decorating smooth caustics), the Pearcey function (decorating cusped caustics), and the hyperbolic umbilic diffraction (decorating the finite-angled corner caustic near the top left of the image). Title of photo is: Bathroom-window caustics The on-screen image was photographed with a compact digital camera, and this contest entry is the unprocessed JPEG file.
—Michael Berry, University of Bristol, United Kingdom
20 Nov 2019