Blood stains are red Ulltraviolet lights are blue Shirt

Initial studies of the chemical rays focused on their ability to stimulate chemical reactions. In 1809, Gay Lussac & Thénard demonstrated that concentrated sunlight was capable of converting a mixture of hydrogen and chlorine gases into hydrochloric acid. In 1815, Planché noted that chemical rays darkened many kinds of metallic salts. Between 1826-1837, Niépce & Daguerre found that silver iodide was especially light-sensitive, and they used this discovery as the basis for their early work in photography. In 1842, Becquerel and Draper independently showed that when sunlight was passed through a prism onto a daguerreotype plate (a gelatin emulsion containing silver iodide), wavelengths between 340-400 nm induced a photochemical reaction. This was the first indication of the spectral extent of UV radiation.During the 19th century, physicists made several important theoretical and empirical contributions that helped to clarify the properties of UV radiation. In 1802, Wollaston expanded on Newton’s earlier observation, that sunlight was comprised of different colors, by showing that sunlight possesses discrete bands of light rather than a continuous spectrum. In 1814, Fraunhofer mapped over 500 bands of sunlight, later called “Fraunhofer lines,” some of which are within the UV region. In 1859, Kirchoff & Bunsen invented the spectroscope and demonstrated that different atoms absorb and emit different wavelengths of light. They speculated that the gaps in the solar spectrum are the result of selective absorption by atoms in the Earth’s atmosphere.

Blood stains are red Ulltraviolet lights are blue Shirt

A major breakthrough in photophysics came in 1865 when Maxwell proposed a theory that light and sound are part of a larger spectrum of energy with wave-like properties. He called them “electromagnetic waves” because he believed that they were generated by the interaction of electric and magnetic fields. In 1882, Maxwell’s theory was confirmed by Hertz who developed a means for measuring microwaves, the first empirical evidence for radiation beyond the UV-visible-infrared spectrum. His results reinforced the belief that electromagnetic radiation travels in waves at discrete frequencies (or wavelengths).The development of artificial lighting provided another source of UV radiation, although this was not appreciated at first. In 1808, Davy invented the “open”; arc lamp using charcoal electrodes attached to a large Voltaic battery. Unfortunately, the charcoal electrodes deteriorated in the process. In 1843, Foucault tried carbon electrodes that were more stable, but the arc was dim. In 1876-77, Jablochkov and Brush bolstered the power of carbon electrodes using the Gramme dynamo and generated the first useful electric arc lamps. In 1898, Bremer introduced fluoride salts into the carbon electrodes that further enhanced their brightness. In 1850, Stokes used aluminum electrodes to produce a “closed” arc lamp in a quartz tube that emitted UV rays to 185 nm. In 1835, Wheatstone invented the mercury (Hg) vapor lamp which was brighter than previous arc lamps, but it was prone to flicker and deterioration. It would take the contributions of many inventors over the next 66 years before Cooper-Hewitt would produce the first commercially viable Hg vapor lamp.