Topics in Particle and Dispersion Science

Improved geometric optics (IGO) combines standard geometric optics (for example, Hecht E 1987) with rigorous electromagnetic theory (for example, Born M and Wolf 1980) to compute scattering in the far-field (for example, Yang P and Liou 1995). The geometric optics method is applied to the surface of the particle to compute the near-field using the Fresnel equations. The near-field, which can be expressed in terms of the tangential electric and magnetic currents, is then mapped to the far-field by applying rigorous electromagnetic theory in the form of the equivalence principle, which replaces the particle by a set of currents on a closed surface surrounding it (for example, Barber PW and Yeh 1975). This method allows the complete description of scattering by non-spherical particles down to relative particle size of about twenty [AJB, © Crown Copyright 2007].