Ultraviolet light in Science, Industry
and Technology
The following are examples of how ultraviolet light is used
in advanced areas. Many to most of these examples use ultraviolet
light beyond the longwave in your black light, but are interesting
to know about.
Irradiation, Purification and Sterilization (Uses UVC)
UVC light, typically at 254 nanometers, is used to irradiate,
purify and sterilize water, air, food, sewage, laboratories,
office buildings, pools and aquariums. Industrially the process
is called Ultraviolet Germicidal Irradiation (UVGI).
Direct and long enough exposure to UVC light can kill, amongst
other things, Anthrax, Typhoid, E. Coli, Tuberculosis, Salmonella,
Dysentery, Staph Infection , Strep, Legionnaire's Disease , Cholera
, Influenza, Hepatitis, Algae, Fungi. The UVC breaks down the
molecular bonds of the organisms, making them unable to reproduce.
There are limitations to UVC as a germicide. There must be
direct exposure to the light for it to work. This means in a
lab or building there may be areas that are missed. Because of
this, laboratories often used UVC in combination with other methods.
UVC is commonly used to purify circulating air, such as in
an office building. While the air is purified at the spot of
exposure, the air can get dirty again with circulation.
There are commercially marketed hand held UVC germicidal lights
for normal people. They are commonly used by travelers to sanitize
hotel and airplane bathrooms, beds, dishes, etc. I've even seen
a UVC toothbrush cleaner.
While one should take due care using UVC light, there are
advantages of UVC over other traditional disinfectant and purification
methods. UVC doesn't effect they ozone, there are no dangerous
fumes like with bleach and ammonia, and runoff won't contaminate
lakes and rivers.
UVA offers about no practical purification, cleaning effect.
UVB offers some. As regular sunlight includes UVB, it does have
some disinfecting effects-such as when hanging wet clothes or
exposing plates to sun on a camping trip. The drying out is also
helpful.
Medicine (UVA & UVB)
Sunlight can cause health problems-- skin cancer, eye problems,
etc--, but light therapy, using UVA and UVB, is used tor treatment
of a number of dermatology conditions, including psoriasis and
eczema. Veterinarians use ultraviolet light to identify ringworm
in pets.
Danish physician Niels Finsen (1860-1904) won the 1903 Nobel
Prize for Medicine for studies of how ultraviolet light could
treat diseases, including Tuberculosis.
Identifying Gems (Uses UVA & UVC)
There are a variety of methods used to identify diamonds, rubies
and other gems. This includes the use of UVA and UVC light. Gems
fluoresce specific colors and brightness under the two lights.
Sometimes a gem fluoresces one color under UVA and another under
UVC. Other tests used include testing hardness, visual light
color and appearance and place of origin.
Ultraviolet astronomy (all ranges of UV)
Ultraviolet astronomy is a part of astronomy that observes and
studies the ultraviolet light given off by stars, planets, galaxies
and the cosmos. As much of this light is beyond UVA and UVB and
is blocked by the earth's atmosphere, the light can only be obseved
from space or the upper atmosphere. UV telescopes are carried
by rockets, the Hubble Space Station and the Space Shuttle. From
the UV light, scientists can deduce the chemical makeup, weight,
temperatures and even age of cosmic bodies.
WWII airplane safety (UVA)
During World War II, airplanes used maps written in UV fluorescent
ink. During dangerous battle situations, the navigator could
read the map without illuminating the cockpit.
Pest control (UVA)
Ultraviolet fly traps, or bug lights, are used to kill flying
insects. The bugs are attracted to the UV light and trapped or
killed with electrical shock.
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