Extrema in the light-scattering indicatrix of a homogeneous spheroid

The formation and migration of the extrema in the angular distribution of t he scattered light intensity with varying size, ellipticity, and refractive index of a homogeneous spheroid oriented with the axis of revolution along the incident light direction are studied analytically and numerically. The Wentzel-Kramers-Brillouin (WKB), Rayleigh-Gans-Debye, Fraunhofer diffracti on, and anomalous diffraction approximations are used for relative refracti ve indices ranging from 1.025 to 1.200. Equations relating the locations of the extrema to the particle parameters are derived. The analysis of the ex trema predicted by the WKB approximation shows that the locations of differ ent minima migrate monotonously when the size of the spheroid is varied. We also discuss the disappearance of the extrema with increasing relative ref ractive index and particle size. (C) 1999 Elsevier Science Ltd. All rights reserved.