Analysis of Light Extinction Characteristics as a Function of Particle Number and Size Distribution

In this study, the effects of the particle number and size distribution on light extinction were analyzed on the basis of experiments and scattering theory. Monodisperse spherical polystyrene latex particles with diameters of 269, 350, and 500 nm were used, and the experimental conditions were set to maintain a constant total sprayed mass. During the experiments, light extinction and particle size distribution were measured. The results showed that under the same mass conditions, the total particle number increased as the particle size decreased, leading to enhanced light extinction. Using the measured particle number and size distribution, the mass-specific light extinction was estimated using the Mie scattering theory, and the estimated and measured light extinction values were compared. This comparison suggested that the single-particle scattering theory may not fully explain light extinction under high-particle-number-concentration conditions. Based on this comparison, an empirical correction factor for light extinction was derived to correct the errors in the single-particle scattering theory under high-particle-number-concentration conditions.