Need simple logical answer in self words Let fc and fv denot

Need simple logical answer in self words.

Let f_c and f_v denote the Fermi distributions of electrons in conduction and valence bands, respectively. Explain why emission process is proportional to f_c(1-f_v) and absorption process is proportional to f_v(1-f_c)?

Solution

Here fc represents the probability of electron being in conduction band and 1-fv represents the probability for valence band being empty. So for emission process, the more number of electrons must be in conduction band and for absorption, more number of electrons must be in valence band in order to excite them to the conduction band. Thats why the probabilities are as the given in above.