By shining laser light through soap bubbles, researchers have demonstrated branching flow in light for the first time. This branching occurs when waves travel through a disordered medium where the typical size of the disordered regions is larger than the wave’s length. Previously, scientists had seen evidence of this phenomenon in electrons, sound waves, and even ocean waves.
Soap bubbles serve as an excellent platform for branching in light because their exceptionally thin film varies in thickness thanks to the interplay of buoyancy, Marangoni effects, and evaporation. It’s also comparable to — but still slightly larger than — the wavelength of light. The experiment is far from simple, though. Lining the laser up with the soap bubble is tough, especially when your bubble is likely to pop! (Video credit: Nature; research credit: A. Patsyk et al.; submitted by Kam-Yung Soh)