A very important requirement for the use of the Kubelka–Munkmodel is the homogeneous distribution, both vertically and hori-zontally, of the absorbed compound in the layer. If the lightabsorption due to the compound is not excessive, it can be as-sumed that only the absorption coefficient, but not the scatteringcoefficient, of the doped medium changes by adding the light-absorbing compound. The absorption coefficient of the system,ktot=k+ki, given by the sum of the absorption coefficient ofthe medium (k) and that of the compound adsorbed on the solidsurface of the medium (ki), is proportional to the molar absorp-tion coefficient of the compound,ei(k) (cm3/mol.cm), and to itsadsorbed concentration Ci(mol/cm3).