Evaluating the accuracy of single-scattering computations by the geometric optics approximation using Platonic solids

The geometric-optics approximation (GOA) has been effectively applied to computations of the singlescattering properties of nonspherical particles. The physical geometric-optics method (PGOM) combines physical-optics effects and the geometric-optics ray-tracing procedure to compute the single-scattering properties of faceted dielectric particles. Apart from numerical errors, the only source of error of the PGOM comes from the GOA applied to the near-field computation. Generally, the GOA becomes more accurate with increasing particle size. However, the characteristic size of a particle that is the most relevant to the accuracy of the GOA has not been investigated thoroughly. In this study, we conduct PGOM computations for the five Platonic solids with different definitions of the size parameter. A Platonic solid is formed by regular polygons with identical shapes and sizes. The PGOM results are compared with benchmark computations by the rigorous invariant imbedding T-matrix method (IITM). The accuracy of the GOA in computing the scattering phase function of a scattering particle is found to be determined by the individual facet size and the maximum dimension of the particle.(c) 2023 Elsevier Ltd. All rights reserved.