Ultraviolet photography Silicon (from which DSLR sensors are made) can respond to wavelengths between 1100-190 nm. Photography based on visible fluorescence induced by UV radiation uses the same ultraviolet illumination as in reflected UV photography. However, the glass barrier filter used on the lens must now absorb or block all ultraviolet and infrared light and must permit only the "visible" radiation to pass. Visible fluorescence is produced in a suitable subject when the shorter, higher energy ultraviolet wavelengths are absorbed, lose some energy and are emitted as longer, lower energy visible wavelengths. UV induced visible fluorescence photography must take place in a
Photoelectric effect certain threshold frequency (typically visible light for alkali metals, near ultraviolet for other metals, and extreme ultraviolet for non-metals), the radiation is absorbed and electrons are emitted. Light, and especially ultra-violet light, discharges negatively electrified bodies with the production of rays of the same nature as cathode rays. Under certain circumstances it can directly ionize gases. The first of these phenomena was discovered by Hertz and Hallwachs in 1887. The second was announced first by Philipp Lenard in 1900. The ultra-violet light to produce these effects may be obtained from an arc lamp, or by burning magnesium, or by sparking