Photochemical reactions are chemical processes that are initiated or driven by light energy, typically from the sun. These reactions often involve the absorption of photons, which can excite electrons in molecules, leading to various chemical changes. A common example is photosynthesis, where plants convert light energy into chemical energy, producing glucose and oxygen from carbon dioxide and water. In addition to photosynthesis, photochemical reactions are essential in many natural and industrial processes. For instance, they play a crucial role in the formation of ozone in the Earth's atmosphere and are utilized in photolithography for creating microchips. Understanding these reactions is vital for advancements in fields like solar energy and environmental science.