Upper row: height stratification of the source function (colored dashed lines), angle-averaged intensity (colored solid lines), and the Planck function (dashed black line) in the FALC atmosphere. The crosses mark the locations at which τ_ν = 1. The intensity of the four wavelength points closest to the rest wavelength is marked with crosses of corresponding color in Fig. 8. The purple line is taken from the wing at 371.85 nm. Second row: contribution functions at wavelengths corresponding to the upper row.