ultravioletta

Ultravioleta, or ultraviolet radiation, is the portion of the electromagnetic spectrum with wavelengths shorter than visible violet light, roughly from 10 to 400 nanometers. It is not visible to the human eye and is typically divided into UV-A (about 315–400 nm), UV-B (about 280–315 nm), and UV-C (about 100–280 nm).

The atmosphere, especially the ozone layer, absorbs most UV-C and a large share of UV-B, so the surface is mainly exposed to UV-A and some UV-B. The Sun is by far the largest natural source of ultraviolet radiation; artificial sources include tanning beds and germicidal lamps, which emit UV in various bands for disinfection or curing processes.

Biological and health effects of ultraviolet radiation are varied. UV exposure can cause DNA damage, leading to skin cancer and eye conditions such as cataracts, and it contributes to sunburn and photoaging. In contrast, UV-B also stimulates vitamin D production in the skin. Organisms have evolved protective mechanisms, and humans use sunscreens, protective clothing, and eyewear to limit harmful exposure.

Applications of ultraviolet light include sterilization and disinfection of water and surfaces, fluorescence-based analyses, forensic techniques, and polymer curing. UV radiation can degrade materials such as plastics and dyes, and excessive environmental exposure can affect ecosystems, including phytoplankton in aquatic systems.

The term derives from “ultra” meaning beyond and “violet,” reflecting its position beyond the visible violet region of the spectrum. The energy of UV photons increases as wavelength decreases, enabling interactions with molecular bonds and biological systems.