Light scattering by particulate media of irregularly shaped particles: laboratory measurements and numerical simulations

We present a light-scattering simulation based on geometrical optics to study the bidirectional reflectance of particulate media observed from laboratory measurements. The simulation model is built so that the arrangement of composing particles of the media and characteristics of the particles (i.e. size, irregularity of shape and refractive index) can be given as parameters. From the results of simulations and comparison with laboratory measurements, we have found the following: (1) The media of irregular-shaped particles show flatness in the angular change of the reflectance compared with those of more rounded particles. (2) The media of smaller particles with diameters of 150μm show brighter reflectance than those of 600μm, similarly as observed in laboratory measurements. (3) The reflectance in small (<30∘) and large (>120∘) phase angles increases with increasing surface porosity (i.e. enhancements of backscattering and forward scattering). The former can be ascribed to the first order of scattering in contrast with the latter to the first plus the second order of scattering, where the first order of scattering is the total sum of the scattered rays from the first particle hit by the incident ray, and the second means that from the second particle hit by the sub-rays from the first particle.