Fractional linear polarization profiles Q/I in forward scattering (μ = 1) as a function of wavelength distance from the center of each line. The standard synthesis (computed with full physical considerations) is represented in solid black (dubbed ${\rho }_Q^K$) and the unpolarized case in dashed red (${\rho }_0^0$). We show results corresponding to syntheses with 10 G (left panels) and 200 G (right panels) horizontal magnetic fields. The K and 8542 Å lines are shown in the upper and lower panels, respectively.