Ultraviolet (UV) light refers to a type of electromagnetic radiation that has a higher frequency and shorter wavelength than visible light, but lower frequency and longer wavelength than X-rays. It is invisible to the human eye, but can be detected by specialized equipment or noticed as it causes a reaction such as sunburn on exposed skin. Ultraviolet light is emitted by the Sun and other stars, and plays an important role in various natural processes like photosynthesis, DNA replication, and the production of vitamin D. It also has several industrial applications including water disinfection, curing of materials, and sterilization.