Stimulated absorption rate depends ona.Number of atoms in lower stateb.Energy of input photonsc.Both of them

The stimulated absorption rate indeed depends on both the number of atoms in the lower state and the energy of input photons. Here's why:

a. Number of atoms in lower state: The more atoms there are in the lower energy state, the more atoms there are that can absorb energy and move to a higher energy state. This means that the rate of stimulated absorption increases as the number of atoms in the lower state increases.

b. Energy of input photons: The energy of the input photons must match the energy difference between the lower and higher states for absorption to occur. If the energy of the input photons is too low, the atoms won't absorb them and move to the higher state. If the energy is too high, it could lead to ionization or other processes. Therefore, the energy of the input photons can affect the rate of stimulated absorption.

So, the stimulated absorption rate depends on both the number of atoms in the lower state and the energy of input photons.