Ultrafioletu

Ultrafioletu refers to a portion of the electromagnetic spectrum that lies beyond visible violet light, with wavelengths approximately from 10 to 400 nanometers. It is commonly subdivided into UV-A (about 315–400 nm), UV-B (280–315 nm), and UV-C (100–280 nm). The boundary with vacuum ultraviolet, which exists at even shorter wavelengths, is strongly absorbed by air and is observed mainly in laboratory or space environments.

The Sun is the primary natural source of ultrafioletu radiation. The Earth’s atmosphere absorbs most of the shorter wavelengths, especially UV-C and much of UV-B, while UV-A reaches the surface in greater quantities. Artificial sources include mercury lamps, UV-C and UV-B lamps, UV LEDs, and tanning beds, which emit varying portions of the spectrum for disinfection, curing, medical treatments, or illumination.

Measurement and detection of ultrafioletu employ radiometric quantities such as irradiance and radiance, often expressed in watts per square meter. The UV Index is a public health metric used to communicate the level of sun exposure risk. Instruments include UV photodiodes, spectrometers, and dosimeters designed to monitor cumulative exposure.

Applications of ultrafioletu span disinfection and sterilization (notably UV-C in water and air treatment), polymer and resin curing, forensic and biological fluorescence, horticultural lighting, and photolithography in semiconductor manufacturing. Biological effects depend on wavelength and exposure: UVA can contribute to aging and DNA damage through reactive oxygen species, while UVB and UVC are more energetic and can cause sunburn, DNA mutations, and skin cancer with sufficient exposure.

Historically, ultrafioletu was identified by Johann Wilhelm Ritter in 1801, who observed rays beyond violet and named them ultraviolet, from ultra- meaning beyond and violaceus meaning violet.