A simple method for determining the extinction ratio of strongly scattering media

In order to determine the extinction ratio k of strongly scattering media, a simple technique for instrumental elimination of the initial curvilinear part of the dependence of optical density D on medium thickness h, D(h) = D1 + kh, where D1 is the apparent optical density of the surface layers of depth hc = 1/k (1/k is the depth of radiation penetration into the substance), is proposed. To this end, two-beam recording is used, with the sample of thickness h placed in the working cell and with the shield of thickness h0, made of the same material, placed in the comparison cell, provided that hc < h0 < h. The extinction ratio is found from the relation k = dD/dh, where dD = D(h)-D(h0) is the difference of the optical densities in the working cell and in the comparison cell and dh = h-h0 is the difference of the thicknesses. For samples with h < hc, two shields of thickness h0 are placed in each cell (in the working cell, in front of the sample and behind it) provided that h0 > hc. In this case, k = dD/h, where dD = D(h + 2h0)-D(2h0).