Glossary

Where the turbidity value is determined by measuring the scattered light intensity, the wavelength of the light used has a certain effect on the results - as do the number of particles and their particle size and refractive index.

The scatter intensity depends partly on the relation between the particle diameter d and the wavelength l; it also increases with the square of the wavelength:

The effect of wavelength changes is inverse to changes of particle size diameter d. But the factor l²  has a damping influence, which means that the scatter intensity does not depend heavily on the wavelength in the visible range. This is illustrated in the following Figure.

Scatter intensity (S) as a function of wavelength l for two particle sizes of SiO2. (1000 ppm, 90°, n=1.48 in water, log. standard dist. with sigma=0.6)