SE formation of EB diagnostics in the ALC7 model atmosphere of Avrett & Loeser (2008) computed with the RH code of Uitenbroek (2001). Left, solid: logarithmic NLTE population departure coefficients b ≡ n/n^LTE as function of height, respectively b_l for the lower level and b_u for the upper level of the line identified in each panel. Left, dashed: logarithmic lower-level populations normalized by the total element density (axis scales to the right). Left, dotted: the same fractional population in LTE. Right: Planck function B_λ (thin solid, the same in all panels), angle-averaged intensity or J_λ (dashed), line source function S_λ (solid). These quantities are plotted as representative temperatures to avoid the Wien sensitivity of the Planck function and so obtain directly comparable scales. For PRD lines (Ca ii  K and Mg ii  k) S_λ and J_λ are shown for line center and the emergent-profile peaks and dips. The three vertical ticks define the heights where total optical depth τ_λ = 3,1,0.3, respectively (in the lefthand column only for line center on the b_l curve). The S<B splits correspond to the b_u<b_l divergences at left. Remarkable: at left the very deep dip in the dashed Hα population curve, the relative flatness of the Ca ii 8542 Å and Ca ii  K population curves, the utter flatness of the Mg ii  k population curve, and the large chromospheric overpopulations from photon suction for the Mg i b₂ and Na i  D₁ lower levels. At right the discordantly high value of S ≈ J for Hα across the temperature minimum from backscattering and the overall similarity of the scattering S ≈ J declines of all lines, including independently scattering PRD wings.