Ultravioletter

Ultravioletter, also known as ultraviolet radiation, is a form of electromagnetic radiation with wavelengths shorter than visible light but longer than X-rays. In vacuum it spans roughly 10 to 400 nanometers and is commonly divided into three bands: UVA (315–400 nm), UVB (280–315 nm), and UVC (100–280 nm).

Most ultraviolet radiation reaching Earth originates from the Sun. The atmosphere, and especially the ozone layer, absorbs a large portion of UVB and all UVC, allowing primarily UVA to reach the surface. Artificial sources include black lights, mercury lamps, UV-curing equipment, and tanning beds.

Ultravioletter interacts with matter and biology in diverse ways. Exposure can cause photochemical reactions in DNA and proteins, contributing to skin cancer and cataracts, while UVA also drives photoaging. UVB is the main driver of vitamin D synthesis in the skin. In materials science, UV exposure can degrade polymers and pigments but is also used for curing coatings and enabling fluorescence in certain substances.

Applications of ultraviolet radiation include disinfection and sterilization with UV-C, fluorescence-based analysis in forensics and biology, curing of resins and coatings, and phototherapy for some skin conditions. Safety practices, such as using sunscreen, protective clothing, and UV-filtering eyewear, are important to reduce health risks.

Measurement and monitoring of ultraviolet radiation rely on the UV index, which estimates the risk of harm from sun exposure for a given location and time. Environmental factors, notably the state of the ozone layer, influence ground-level UV flux and related health and ecological effects.