The photochemical reaction is nothing more than a chemical process that begins with light being absorbed as a source of energy. While the molecules absorb light, temporary peak states would be initiated, and there would be significant differences between the model molecules' physical and chemical properties. The classification of photochemical reaction pathways should be used to and subsequently the rate constants of all pertinent photophysical and photochemical processes provide details on the composition, fate, lifetimes, and reactivities of any reactive intermediates. It is a subfield of chemistry that focuses primarily on the rates and mechanisms of reactions that occur when reactants are exposed.