Photochemistry is concerned with chemical changes that may be brought about by the absorption of light [1]. In principle, the photochemical reac-tion of a substance proceeds according to two laws. The first one was proposed by Grotthus and Draper in 1818 and states that “a chemical reac-tion of a certain substance only takes place via the excitation of the mole-cule by the absorption of light quantum of sufficient energy.” The second law is the photochemical equivalent law proposed by Einstein in 1912 which states that “each photon or quantum absorbed activates only one molecule” [2].