Principle of particle size testing by light transmission method

From Stokes' law, it can be known that as long as the sedimentation velocity of a particle is measured, the particle size of the particle can be obtained. In the actual measurement process, it is difficult to directly measure the particle sedimentation velocity. Therefore, during the sedimentation method particle size testing process, the rate of change of the light intensity passing through the suspension with time is often used to indirectly reflect the particle sedimentation velocity. According to Beer's law, the quantitative relationship between light intensity and particle size at a certain moment is:

In this way, we can obtain the particle size distribution by measuring the light intensity at different times to obtain the change rate of the light intensity.