Refractive caustic network

by Konstantinos Kourtidis, Demokritus University of Thrace, Xanthi, Greece

This video shows the so-called refractive caustic network. A wavy water surface (the sea, in this image) projects patterns of sunlight onto nearby surfaces (the bottom, in this image). The surface of the water acts as a series of positive and negative lenses. The positive ones focus sunlight onto the bottom (creating the moving lines of light) while the negative ones refract light out of the beam.