J4 ›› 2010, Vol. 37 ›› Issue (4): 731-736.doi: 10.3969/j.issn.1001-2400.2010.04.027

• Original Articles • Previous Articles     Next Articles

Rainbow angle analysis of a homogeneous spheroid

LI Xiang-zhen;HAN Xiang-e   

  1. (School of Science, Xidian Univ., Xi'an  710071, China)
  • Received:2009-03-24 Online:2010-08-20 Published:2010-10-11
  • Contact: LI Xiang-zhen E-mail:lllleo2002@yahoo.com.cn

Abstract:

A general ray-tracing method for homogeneous spheroids with the arbitrary aspect-ratio is presented on the basis of geometrical optics, and is employed to study the primary rainbow angle of spheroids with a larger aspect-ratio at an arbitrary incidence. For the prolate spheroid normally illuminated by plane waves, when the aspect-ratio is in a certain range, no primary rainbow angle exists. The research shows that the aspect-ratio range increases with the refractive index of the spheroid. For the oblique incidence, the symmetry of two primary rainbow angles varies with the tilt angle of the incident plane wave in (0°~360°). The primary rainbow angle of the oblate spheroid at the normal incidence is similar to that of the sphere. For the oblique incidence, the variation of the primary rainbow angle of oblate spheroid is opposite to that of the prolate spheroid. The results lay the theoretical groundwork for granularity measurement of the spheroidal particle.

Key words: light scattering, geometrical optics, ray tracing, spheroidal particle