Light backscattering by fine non-absorbing suspended particles

In this paper, light backscattering measurements with fine silica, alumina, titanium dioxide and polystyrene latex particle suspensions for solids volume fraction φ between 10−6 and 0.3 are presented. For small φ, the measured normalized backscattered intensity can be expressed as a power law of φ with an exponent of about 0.85±0.05. Even for the smallest examined φ, multiple scattering takes place as is proved by Monte Carlo simulations and analytical calculations. For high φ, the total inverse transport mean l̃*−1 free path is found to be the determining parameter. Comparison between experimental data and the diffusion approximation of the radiative transfer theory reveals good agreement for l̃*−1>10 cm−1. In this case, a mean particle diameter can be determined supposing a particle size distribution (PSD) and knowing the volume fraction and relative refractive index of the particles.