Concept
The concept of UV Tube is based the ability of ultraviolet light to kill infectious agents by disrupting their DNA. It was initially developed under an "open source" model at the Renewable and Appropriate Energy Laboratory at the University of California, Berkeley.
The form and composition of the UV Tube can vary depending on the resources available and the preferences of those building and using the device. However, certain geometric parameters must be maintained to ensure consistent performance.
Fluorescence
Fluorescence is the emission of light by a substance that has absorbed light or other electromagnetic radiation. It is a form of luminescence. In most cases, the emitted UV tube has a longer wavelength, and therefore lower energy, than the absorbed radiation. However, when the absorbed electromagnetic radiation is intense, it is possible for one electron to absorb two photons; this two-photon absorption can lead to emission of radiation having a shorter wavelength than the absorbed radiation. The emitted radiation may also be of the same wavelength as the absorbed radiation, termed "resonance fluorescence".
The most striking examples of fluorescence occur when the absorbed radiation is in the ultraviolet region of the spectrum, and thus invisible to the human eye, and the emitted light is in the visible region.
Fluorescence has many practical applications, including mineralogy, gemology, chemical sensors (fluorescence spectroscopy), fluorescent labelling, dyes, biological detectors, and, most commonly, fluorescent lamps.
