Write a decomposition chemical reaction caused by light?

A decomposition reaction caused by light is the photographic reaction of silver bromide (AgBr). When silver bromide is exposed to light, it decomposes into silver (Ag) and bromine (Br₂). This reaction is fundamental in traditional photography, where light-sensitive silver halide crystals react to form a latent image.

The balanced chemical equation is: $$2\mathrm{AgBr}\stackrel{\mathrm{light}}{\to }2\mathrm{Ag}+\mathrm{Br}{}_2$$

In this reaction, light provides the energy required to break the bonds in silver bromide, resulting in the formation of metallic silver (which appears as a dark image) and bromine gas. This process is irreversible and is the basis for capturing images on photographic film.