Answer to Question #94267 in Physical Chemistry for Abhishek

Question

State the two laws of photochemistry. Define
quantum efficiency for the formation of a
product. Why do some reactions show very high
quantum efficiency ?

Answer 1

The First Law of Photochemistry :The light must be absorbed for photochemistry to occur.

The Second Law of Photochemistry : For each photon of light absorbed by a chemical system, only one molecule is activated for a photochemical reaction.

Quantum efficiency"(Q.E.) is the ratio of the number of carriers collected by the solar cell to the number of photons of a given energy incident on the solar cell.

For reactions the term used is generally Quantum Yield. Quantum yield is defined as “the number of molecules of the substance undergoing photochemical change per quantum of radiation absorbed.

High quantum yield may be due to : The active molecules, produced after absorption of radiation, may collide with other molecules and activate them which in turn activate other reacting molecules.