Nearultraviolet

Near-ultraviolet (NUV) refers to the portion of the electromagnetic spectrum that lies between the visible range and the deeper ultraviolet. In many contexts it covers wavelengths roughly from 300 to 400 nanometers, i.e., just beyond the violet end of visible light. Some fields define the boundaries slightly differently, and in astronomy the term is often used in relation to adjacent ultraviolet bands such as near-UV and far-UV.

Observations in the near-UV are influenced by the Earth's atmosphere, which absorbs a significant fraction of ultraviolet radiation, particularly at shorter wavelengths. As a result, many NUV measurements are made from space or from high-altitude platforms, using detectors and optics designed to be sensitive to ultraviolet photons while minimizing longer-wavelength contamination. Detectors used for NUV work include UV-enhanced CCDs, photomultiplier tubes with UV sensitivity, and specialized microchannel plate devices.

NUV is applied across several disciplines. In astronomy, it is used to study hot, young stars, star-forming regions, accretion processes, and the properties of dust and gas in galaxies and the interstellar medium. In planetary and atmospheric science, near-UV data help characterize surface composition, aerosols, and scattering properties. In biology and materials science, near-UV photons drive photochemical reactions, fluorescence, and curing processes, and are used in spectroscopic techniques to probe molecular structure.

The term is closely related to, but distinct from, adjacent spectral regions such as the visible, near-infrared, and the deeper ultraviolet bands.