Light scattering and extinction in polydisperse systems

A simple approach to predict transmittance spectra of polydisperse systems is recalled and applied to various model systems (spinel-like particles in water, pores in a spinel-like matrix) and real systems (spinel in water, diamond in water, amorphous carbon soot in isopropanol) in order to investigate principal effects of size distributions (normal/lognormal, narrow/wide, monomodal/bimodal, shift of mode positions, shift of mode heights) and optical properties (refractive index contrast, with or without absorption) on the in-line transmittance. A comparison of predicted and measured spectra showed that size distributions with more small particles cause a more significant decrease in transmittance (at least for sufficiently short wavelengths) and that laser diffraction may seriously underestimate the amount of small particles (for absorbing particles, for which the influence on transmittance is enormous, a difference of up to 30% in absolute transmittance measured via spectrophotometry has been found against predictions based on laser diffraction results).