Light scattering through 2D Plateau borders and foams

A ray-tracing method based on geometrical optics is proposed to study optical properties of foams in two dimensions. This reveals the complexity of the propagation of light through films and Plateau borders on the bubble scale. We simulate the intensity distribution of light emerging from a pair of Plateau borders confined in a Hele-Shaw cell. Our result that the width of the image scales with the distance between the cell and an observation screen in the form of a power law is useful for the interpretation of experimental data. We also compute the average distance that a ray of light travels within a triangular Plateau border as being 1.22 times the path length as for the case where no scattering occurs. Our simulations of light propagation through 2D foams, simulated using our hybrid lattice gas model, reproduce key experimental results for 3D foams, such as the variation of the transport mean free path with liquid fraction of the foam. The simulations show the importance of the Plateau borders for the propagation of light in a foam.