Continuum optical depth as a function of wavelength in the optical range for each atmospheric layer in transmission geometry considering the TP model number 047. The values shown on the left-hand side give the logarithm of the pressure of the corresponding layer. For visualisation purposes, the pressure level is shown for every second layer starting from the top of the atmosphere and stop where the continuum optical depths of the layers start overlapping. To guide the eye, the red horizontal line is at 2/3, while the vertical blue dotted lines indicate the position of the Hα and Hβ lines.