Rainbow phenomena and the detection of nonsphericity in drops

Liquid drops were levitated and deformed with acoustic techniques and illuminated with monochromatic light. Changes in the rainbow-angle scattering induced by the deformations were detected. Reflected and refracted rays form an interference pattern that changes with shape and the angle of Airy's diffraction pattern shifts. A calculation by W. Möbius [Ann. Phys. (Leipzig) 33, 1493 (1910)] was modified to facilitate the use of these changes for the measurement of micron amplitude shape oscillations of millimeter radius drops.