Abstract
We compare a recently developed coherent-scattering model for the reflectance of light from a turbid colloidal suspension of particles with experimental measurements. The experimental data were obtained in an internal reflection configuration around the critical angle using a glass prism in contact with a monodisperse colloidal suspension of latex particles, and a polydisperse suspension of TiO2 particles. First, we review the coherent scattering model and extend it to the case of polydisperse suspensions in an internal reflection configuration. The experimental data is then compared with results of the coherent scattering model and results obtained assuming that the colloidal system can be treated as a homogeneous medium with an effective index of refraction. We find that the experimental results are not compatible with the effective medium model. On the other hand, good fits to the experimental curves can be obtained with the coherent scattering model.
Highlights
When light, traveling in a transparent homogeneous medium, strikes the flat interface of a medium with random inhomogeneities, scattered light appears on both sides of the boundary
We include in the figure curves calculated with the coherent-scattering model (CSM) and the isotropic effective-medium model (IEMM)
We present three graphs for three different values of f : 0.38%, 0.70% and 1.20%. In this case the polarization of light was TE and we compare the experimental data with results from CSM and IEMM for polydispersed systems assuming a log-normal size distribution
Summary
When light, traveling in a transparent homogeneous medium, strikes the flat interface of a medium with random inhomogeneities, scattered light appears on both sides of the boundary. The total intensity (IT) can be separated, in general, as the sum of a coherent (Ic) or direct component, and a diffuse (Id) or incoherent one. Defining the coherent intensity as the magnitude squared of the mean field, Ic =||2, the diffuse intensity is given by Id = - Ic, where the angled brackets indicate an average over an ensemble of realizations of the random inhomogeneous medium. The fraction of the original power that goes into the diffuse component depends on the turbidity of the sample and the angle of incidence. A medium is regarded as homogeneous when the diffuse component is negligible, whereas a medium is considered turbid when the diffuse component can be detected. In homogeneous media the coherent or mean field coincides with the macroscopic field
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