Hi Is it technically sound to state that the rate of absorption of photons at a given frequency is proportional to the number of photons at that frequency? most statements of the B coefficients seem to focus on molecular state populations, but I'm reasoning that for every state change n1--->n2 there must also be one less photon? edit- is it also sound to say the number of photons at that frequency is proportional to the intensity of light? I think this should be correct, just double checking. Brain has switched off.