Photo Equivalence Law

A fundamental idea pertaining to light-induced chemical reactions is the photochemical equivalency law, which states that for every unit of radiation received, a molecule of the material responds. The Greek letter nu is used to represent the frequency of electromagnetic radiation, and it is used to represent a quantum, which is a unit of electromagnetic radiation with an energy equal to the product of a constant (or Planck's constant - h) (v). In chemistry, gramme moles are used to indicate quantitative measurements of compounds. An individual gramme mole is made up of 6.022140857 1023 (Avogadro's number) molecules. The photochemical equivalency law may therefore be rephrased as follows: For every mole of the substance that reacts, 6.022140857 1023 quanta of light are absorbed. The fundamental mechanism of a light-induced reaction—i.e., the initial chemical change that comes directly from the light absorption—will be subject to the photochemical equivalency law. The initial process in the majority of photochemical reactions is often followed by so-called secondary processes, which are regular interactions between the reactants and do not necessitate the absorption of light. As a result, these reactions don't seem to follow the one quantum - one molecule reactant relationship. This law is further limited to conventional photochemical reactions involving light sources of moderate intensity; high-intensity light sources, such as those used in laser experiments and flash photolysis, are said to cause the so-called bi-photonic reactions, which refer to the absorption of two photons by a molecule of a substance.