Evolution of the model echo total flux (in the magnitude scale) as a function of the optical thickness, τ₀, along the line of sight of the central source (upper panel) and the anisotropy factor,  ⟨ cosθ ⟩ , (bottom panel). Dashed curve in both panels: the light curve of the central source (the same as in the upper panel of Fig. 4). Full curves in the upper panel: the light echo flux evolution with  ⟨ cosθ ⟩  fixed at 0.6 but for τ₀ varying from 0.05 (bottom curve), through 0.1, 0.2, 0.3, and 0.5 (uppermost curve). Full curves in the bottom panel: the light echo flux evolution with τ₀ fixed at 0.2 but for  ⟨ cosθ ⟩  varying from 0.0 (bottom curve), through 0.2, 0.4, 0.6, and 0.8 (uppermost curve)