What is photolytic decomposition?

Photolytic decomposition is a chemical reaction in which a compound breaks down into simpler substances when exposed to light. Decomposition reactions are chemical changes where one substance breaks down into two or more substances.

One special type of decomposition reaction is called photolytic decomposition, which happens under the influence of light energy, usually sunlight or ultraviolet (UV) light.

Definition

Photolytic decomposition is the process in which light energy provides the activation energy required to break chemical bonds, resulting in simpler products. This is why it is also called photodecomposition or photolysis.

Examples of Photolytic Decomposition

• Silver chloride (AgCl): AgCl → Ag + Cl₂ (on exposure to sunlight, AgCl breaks down into silver and chlorine gas).
• Silver bromide (AgBr): AgBr → Ag + Br₂ (used in photography).
• Ozone (O₃): O₃ → O₂ + O (decomposition by UV radiation in the atmosphere).

Applications

• Photography: Silver halides decompose under light, forming images on films.
• Photosynthesis: Light splits water molecules into hydrogen and oxygen in plants.
• Environmental Science: Breakdown of pollutants under sunlight helps reduce smog.