Bubble optics: upward emerging ray paths.

Light scattered by floating bubbles is a fascinating everyday phenomenon and a relevant issue for climate science and remote sensing. Here, we discuss light scattering in the upward hemisphere in the geometrical optics (GO) approximation for plane wave incidence with various inclinations on isolated floating bubbles of various sizes, using numerical and analytical caustic theory methods. We identify and discuss the relevant ray paths and explain the caustic evolution observed on a screen placed close to and above a large bubble.