Effects of the dust optical depth on the Lyα line profiles emerging from three different static shell geometries: a homogeneous shell (n_IC/n_C = 1.0 – top line), a weakly clumpy shell (n_IC/n_C = 0.01 − middle line), and an extremely clumpy shell (n_IC/n_C = 0.00 – bottom line). Both the weakly and the extremely clumpy shell geometries are those studied, respectively, in Figs. 14 and 17. We thus adopt here the same physical conditions: FF = 0.23, CF = 0.997, = 2 × 10²⁰/cm^-2, v_exp = 0 km s^-1, and b = 40 km s^-1. Note the variable scales of the different sub-panels. An enhancement of EW(Lyα) (produced by the Neufeld effect) occurs only for the physical conditions corresponding to the bottom right panel ( = 3).