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 or energy transformations. Photochemical reactions are essential in various natural processes, such as photosynthesis in plants, where sunlight is converted into chemical energy. The study of photochemistry also has practical applications, including the development of solar cells and photodynamic therapy for treating cancer. Understanding how light interacts with matter helps scientists design better materials and improve energy efficiency in various technologies, making photochemistry a vital area of research in modern science.