Kubelka-Munk theory also

These coefficients have the dimension of reciprocal length (Mills, 1988), in this context, cm Kubelka and Munk (1931) described the optical properties of pigments by employing the parameters a and r. The Kubelka-Munk theory is the basis of diffuse reflection spectroscopy (Sec. 6.4). We have extended the Kubelka-Munk approach in order to describe the Raman scattering of crystal powders (Schrader and Bergmann, 1967). The results can also be applied to liquids and transparent solids. The procedure is as follows ... 

The Kubelka-Munk theory relates the extinction coefficient to the reflection. In the simplest case, it is assumed that light is only scattered in two directions in the incident and in the backward direction for an incident ray normal to the surface of the test sample. Also, both incident light and emitted light are diffuse. According to Kubelka and Munk, then. 

This theory relates to the direct observation of the scattering of a single particle as compared to the Kubelka-Munk theory, which relates to multiple scattering between particles. Mie theory also takes into account the absorption, which the particle may also exhibit. 

Mie Theory n Theory which relates the scattering of a single spherical particle in a medium to the diameter of the particle, the difference in refi"active index between the particle and the medium, and the wavelength of radiant energy in the medium which is incident on the particle. This theory relates to the direct observation of the scattering of a single particle as compared to the Kubelka-Munk Theory, which relates to multiple scattering between particles. Mie Theory also takes into account the absorption which the particle may also exhibit... 

Simmons (1975) compared various theories of diffuse reflectance. He introduced a modified remission function, which explains deviations from linearity when F(p) is plotted versus k. He also concluded that the Kubelka-Munk function is proportional to the absorption coefficient k as obtained from transmission measurements for "weakly absorbing samples." Unfortunately, most literature is vague in that "weak" or "strong" absorption is not specified. One value given for "weak" is F(p) < 1 (Kellermann, 1979). 

As several researchers have shown empirically, the use of —log(reflectance) can provide, analogous to a transmittance measurement, a linear relationship between the transformed reflectance and concentration, if the matrix is not strongly absorbing as can be found for many samples studied by near-infrared spectroscopy. This issue is presented in detail below. A different approach based on a physical model was considered for UV/VIS measurements and later also applied within the mid-infrared. A theory was derived by Kubelka and Munk for a simple, onedimensional, two-flux model, although it must be noted that Arthur Schuster (1905) had already come up with a reflectance function for isotropic scattering. A detailed description of theoretical and practical aspects was given by Korttim. The optical absorption... 

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