What is it? It is a portion of the Ultra-Violet Spectrumthat is invisible to our eyes. We can not distinguish it. However, when thisradiation impinges on certain materials visible light is emitted and this isknown as “fluorescence.” Fluorescence is visible to the human eye, in that itmakes an object appear to “glow in the dark.”There are several sources of ultra-violet light. These sources are: thesun, carbon arcs, mercury arcs, and black lights. In most cases, the production of ultra-violet light creates a reasonable amount of heat.
Many materials exhibit the peculiar characteristic of giving off lightor radiant energy when ultra-violet light is allowed to fall upon them. This iscalled luminescence. In most cases, the wave length of the light radiated islonger than that of the ultra-violet excitation but a few exceptions have beenfound. The quantum theory attempts to explain this property by contending thata certain outside excitation causes an electron to jump from one orbit toanother. It is then in an unstable environment causing it to fall back into itsoriginal orbit. This process releases energy, and if it is in the visible partof the spectrum, we have a transient light phenomenon. Ultra-violet light is an exciting agent which causes luminescence to occur.
There are many materials which exhibit fluorescent characteristics. Many of which are even organic. Teeth, eyes, some portions of the skin, andeven blood exhibit fluorescent qualities. Naturally occurring minerals such as:agate, calcite, chalcedony, curtisite, fluorite, gypsum, hackmanite, halite,opal scheelite, and willemite, also have similar characteristics. Thesematerials can be used in industries. The radiance of ultraviolet light is measured in units called”Angstrom.” The intensity of ultraviolet fluorescence is the greatest betweenthe 5000 and 6000 range. This being the range between the green and yellow hues.
Ultra violet light is not readily visible. It is not visible becausecertain materials reflect it. Ultra-violet light is made visible due to thefact that it causes a reaction at the atomic level. When it strikes the atom,some of the electrons are sent into other orbits. This then creates an unstable situation which causes the electron to fall back into its place. This processproduces energy, and this is what is seen. This discharge of energy is whatcreates the “glow” that is seen. I had no idea that light could cause such anstrong reaction on something. That something being an atom is even moreprofound. Ultraviolet light causes the atom to lose a subatomic particle thenregain it, and give off energy in the form of visible light. This is justamazing.