Ultraviolet light was discovered in 1801 by German physicist Johann Wilhelm Ritter. It is a type of electromagnetic radiation with wavelengths shorter than visible light but longer than X-rays, between 300 to 400 nanometers. UV radiation can damage components of paper, photographs, inks and other materials by causing photoionization which alters atoms and molecules. The UV spectrum is divided into UVA, UVB, and UVC bands with different wavelengths. The sun is a major natural source of UV rays, with UVA making up most of the UV that reaches Earth. UV exposure can benefit humans by producing vitamin D but too much causes sunburns and skin damage. UV light has applications in security, forensics