Light caustics from rippling water

The caustic patterns produced when light is refracted or reflected by a rippling water surface have certain typical features, but detailed structure is normally unresolvable. An analytic form consisting of a pair of plane waves crossing each other is used to represent such water surfaces, and their caustics computed, revealing fine structure in commonly observed caustic patterns. These fine structures have been confirmed experimentally, in vivo by using a ripple tank and in vitro with glass slides grooved to simulate water waves.