Observations of light backscattered from air bubbles in a viscous liquid demonstrate an enhancement due to axial focusing. A physical-optics approximation for the cross-polarized scattering correctly describes the spacing of regular features observed. The non-cross polarized scattering is not adequately described by a single class of rays.
©1981 The American Physical Society
Langley DS, Marston PL. 1981. Glory in optical backscattering from air bubbles. Physical Review Letters 47(13): 913-916. https://doi.org/10.1103/PhysRevLett.47.913