What is Ultra Violet?
An important matter to realize is that Ultra Violet is not a single entity, but is a wide band of
wavelengths. The chief natural source of UV is the sun. In fact, about 9% of all energy emitted by
the sun is UV. Most of which is in the region between 300-400 nm. Artificial sources of UV include
incandescent, gas discharge, low pressure mercury, medium pressure mercury, metal halide,
electrodeless and xenon lamps.
An interesting characteristic of UV radiation occurs when it falls upon certain substances known
as phosphors, where it causes the phosphors to emit specific radiation. This phenomenon is
known as fluorescence. Everyday fluorescent lighting is basically a UV lamp constructed of a type
of glass bulb that block UV rays. The inside of the bulb is coated with a thin layer of fluorescent
material that receives UV generated by the lamp and in turn emits a visible light in return.
Scientifically speaking, ultra violet is electromagnetic radiation in the part of the spectrum
between x-rays and visible light. It differs from light only in that its wavelengths are too short to be
seen by the human eye. The boundary between visible light and UV light is usually taken to be
radiation with a wavelength of 400 nanometers (4000 angstroms). It is customary to divide the UV
spectrum into near UV 300-380 nm) and far (200-280 nm), the adjectives near and far indicating
the relative distance from visible light.
One effect of UV energy upon certain substances is a phenomenon that takes place at the atomic
level. UV energy affects the charge carried by the proton orbiting the nucleus of an atom. This
forces the proton into a different orbit and produces the glow we call ultra violet fluorescence.
Fluorescence, then is produced by the material itself when its atoms are excited by UV energy.
The material is the light source. When the UV energy is turned off, the proton resumes its natural
orbit and we no longer see it glow.
One of the most popular and well known applications is the use of UV lights to fluoresce additives
and marking agents. In many industries, invisible identification marks such as signatures,
handstamps, product codes and laundry marks can be detected with UV light. This same
technique is also used to reveal differences between genuine and counterfeit documents.
Fluorescence of oil and air conditioning additives are used to detect leaks in assembly line and
garages.
The use of UV has also made many contributions to the medical field. UV radiation can be used
to diagnose certain skin diseases and can be used to treat skin conditions such as acne and
eczema. Another important biological effect of UV radiation is its ability to produce vitamin D from
the ergesterol in the skin. It is this reaction that allows sunlight to prevent and cure rickets. In
dental diagnosis, UV fluorescence is used to reveal caries, plaque and the presence of gum
disease.
The shorter UV wavelengths have the ability to destroy bacteria and viruses. The Food & Drug
Industry as well as many laboratories, hospitals and general industries use ultra violet radiation to
sterilize water, air and any material which requires extremely sanitary conditions. Because a
considerable amount of research is centered around ultra violet reactions and fluorescence
techniques, UV will continue to play an important part in the fields of medicine, biotechnology and
water treatment.
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