Angular scattering measurements obtained with a polar nephelometer employing a linearly polarized laser source are used to examine the general scattering behavior and rainbow generation of pendant water drops, a type of near-spherical particle that has certain similarities to the shape of distorted raindrops. Comparison of the experimental data with theoretical predictions of spherical drop scattering reveals that in many respects the near-spherical particles behave like spheres when the measurements are performed in the horizontal scattering plane, the plane in which the drops display circular cross sections. Furthermore, the angular positions of the rainbow intensity maxima corresponding to the main rainbow peak and supernumerary bows are shown to be predicted accurately by the approximate Airy theory for both the primary and secondary rainbows. Pendant drops whose shapes are significantly elongated in the vertical direction are indicated to generate anomalously strong rainbows from three or more internal reflections. The implications of these findings to rainbow formation in the atmosphere are discussed.
© 1979 Optical Society of America
Kenneth Sassen, "Angular scattering and rainbow formation in pendant drops," J. Opt. Soc. Am. 69, 1083-1089 (1979)