With small rectangular cross-section incident light beam(SRCSILB) focused by a flat-convex lens and all the lights propagating through a straight-line-type optical wave-guide cell(OWGC) by total reflection within its meridian planes, an expression was induced for the calculation of absorbance A of OWGC. According to this expression and a number of given parameters, numerical calculations were conducted and Fig. 3 was drawn. Very good linearities of the dependence of A on the concentration C of specimens and the length l of the OWGC are obtained for all the linear lines. These results indicate again that Wei Lei et al. and Dasgupta's conclusion of nonlinearities between A and C or l is not unconditionally tenable.
