Distribution of absorption depths from the empirical Monte Carlo (EMC) simulation at the Na doublet, Hα, and K D₁ lines, along with three control lines (Mg I 5183.604 Å, Ca I 6122.217 Å, Ca I 6162.173 Å). The control lines are sensitive to stellar activity. The absorption depths are measured in two 0.4 Å passbands for Na doublet, a 0.35 Å passband forHα, a 0.55 Å passband forK D₁, and a 0.4 Å passband for the three control lines, respectively. The red, green, and blue distributions correspond to the “in-out”, “in-in”, and “out-out” scenarios detailed in Sect. 4.3, respectively.