The scattering of light by turbid media.–Part I

The investigation which follows was undertaken with the object of arriving at a theory of the scattering of light by dense turbid media, which would be applicable, in particular, to opal diffusing glasses. The theory is developed on fairly general lines and applies to a system composed of a large number of similar spherical particles of a dielectric suspended in a by medium, provided the relative refractive index is not far from unity. He expressions derived show how the total transmission and reduction of a sheet of a medium containing the particles depends on the following variables; the refractive index of the medium, the side and number of the particles and their refractive index, the wave-length of the incident light and its distribution, that is whether it is diffuse or in the form of a parallel beam, the absorption coefficient of the medium in which the particles are suspended, and the thickness of the sheet. In Part I the general theory is developed, and in Part II numerical values of the necessary coefficients are computed, As a check on the theory, the size and number of the particles in a certain opal glass are deduced from photometric observations of its transmission and rejection. These calculated values are shown to be in agreement with those obtained by direct observation.