A statistical analysis is made for the extinction of radiations in suspensions, whereby the whole range of possible particle concentrations is covered. The extinction signals are characterized by their average value and by a characteristic length of fluctuation. For simplicity, the considerations are restricted to geometric ray propagation in dispersions of perfectly absorbent, monosized spherical particles. An extinction equation is derived, which reduces to Lambert-Beer's law in the limit of low particle concentrations. For higher concentrations, significant deviations from Lamberg-Beer's law due to steric particle-particle interactions are predicted. The characteristic length of the fluctuations is a function of particle diameter and transmission and has a broad minimum with medium transmissions, allowing for maximum resolution with measurements in this range.
