Photochemical reaction

A photochemical reaction is a type of reaction that happens when light energy is used to change one substance into another. Whenever something is exposed to light, that light can create changes in the material by providing energy to the molecules. When the molecules have enough energy, they can react with each other in a new way. This kind of reaction needs light to work, and the light needs to have just the right amount of energy in order for it to happen.