Critical-angle scattering of laser light from bubbles in water: measurements, models, and application to sizing of bubbles

Critical-angle scattering of laser light from bubbles was photographed, and angular structures in the far-zone intensity are compared with models. The radii of the freely rising bubbles were in the 26.4–814-μm range. Deviation from sphericity for the rising bubbles is considered. Diffraction effects make simple geometric optics inadequate near the critical angle. Coarse-structure intensity oscillations show agreement with a physical-optics approximation and with Mie theory. Measurements agree with derived expressions for the angular spacings of fine structure and contrast modulations. Uses of these structures in different bubble-sizing methods are discussed. The locations of scattered-wave virtual sources are modeled.