At the opposite end of the spectrum of color, rays shorter than the violet are present in sunlight. These shorter rays, also invisible to us, produce Vitamin D in our bodies, and they have a tanning effect on our skin. These are the rays known to us as Ultra-Violet rays.

Light from the sun is measured not in inches, feet, or yards, but in a very small unit called an Angstrom Unit, approximately 1/4,000,000,000 of an inch. This unit measurement is not once of intensity or amount, but of the length of the light wave (from peak to peak), and it is this wavelength which determines the effect of the radiation energy.

The visible rays are approximately between 4,000 and 8,000-Angstrom Units. At one end, roughly between 8,000 and 25,000-Angstrom Units, are the Infra-Red rays. At the other end, approximately between 2,000 and 4,000 Angstroms Units are the Ultra-Violet rays. In other words, wavelengths of light at about 8,000-Angstrom Units appear Red in color. Longer waves are invisible. Wavelengths of light at 4,000-Angstrom Units appear Violet in color. Shorter waves are invisible. So we see that sunlight produces at least these three types of light: Visible ("White") Light, so we may see and determine colors; Infra-Red (Invisible) Light (we feel the heat of the sun); Ultra-Violet (Invisible) Light, which produces the phenomena of "Sun tanning".

Through research and science, man has been able to provide himself with artificial sources of Ultra-Violet light. In addition to its sun-tanning effect, Ultra-Violet light or, as it is popularly called, "black light" produces interesting effects on certain substances which we term "fluorescence" and "phosphorescence".

The explanation of Fluorescence and Phosphorescence is rather technical, but if we eliminate all the technical details for the present and attempt to explain these two phenomena in simple terms, we should be able to have a fairly good idea of what causes it. It is common knowledge that all matter is composed of atoms, and each atom is composed of smaller particles (neutrons, electrons, etc.) According to science, the electrons revolve around the nucleus of the atom in fixed orbits. Once it has changed its orbit, the electron proceeds to lose a small amount of energy in the form of heat as it returns to its original orbit. The energy is then re-radiated at a longer wavelength, and it is this re-radiated wavelength which determines the color of fluorescence.

While this entire process of collecting energy, moving into new orbits, re-radiating the energy, and returning to the original orbits takes place in a fraction of a second, we only see the light while the substance is being exposed to the stimulus of ultra-violet or black light. This phenomenon is referred to as Fluorescence.

Some substances are slower than other in their reaction, and their electrons remain in their unnatural orbits for appreciable lengths of time. In these cases, we will continue to see the light after the ultra0violet light source has been removed. These substances will then continue to glow even in absolute darkness. This is the phenomenon we term Phosphorescence. The "after-glow" period varies with each substance.

Although this explanation of these two phenomena is not technically correct, this will give you an idea of what happens. Thus, certain pigments absorb sunlight throughout the day and will often appear glowing. For his own practical purposes, man has taken this phenomenon of fluorescence and adapted hundreds of materials for his own use. Paints, dyes, lacquers, and scores of additional materials have been treated to bring out a whole range of fluorescent and phosphorescent effects, duplicating the complete range of visible colors available in the spectrum.

Risk Reactor is one of the leaders in the field of exploration and development of phosphorescent and fluorescent materials. Applications of these phenomena are widely accepted throughout the world. Industry, medicine, theater, agriculture, military, and advertising are some of the fields that have found an every-increasing use of black light, fluorescent and phosphorescence. We will be pleased to answer any questions you may have pertaining to our products and their applications. Email us at sales@riskreactor.com for more information.