Photochemistry is the branch of chemistry that studies the chemical reactions and processes that occur when molecules absorb light. This field explores how light energy can initiate changes in chemical structures, leading to new substances. Photochemical reactions are essential in various natural processes, such as photosynthesis in plants, where sunlight is converted into chemical energy. In addition to natural processes, photochemistry has practical applications in areas like photovoltaics, which convert sunlight into electricity, and phototherapy, used in medical treatments. Understanding photochemistry helps scientists develop new materials and technologies, including solar cells and light-sensitive dyes.