Ultraviolet (UV) Radiation: Radiant energy in the range of about 100-380 nanometers (nm.) For practical
applications, the UV grand is broken down further as follows:
Bactericidal (germicidal) 220-300nm
Erythemal (skin reddening) 280-320nm
“Black” light 320-400nm
The International Commission on Illumination CIE defines the UV brand as UV-A (315-400nm
UV-B (280-315nm) and UV-C (100-280nm.)
More and more people are watching television and computer screens every day. The cathode-ray tubes that form these screens emit not only visible light but also a good deal of ultraviolet and even “soft” (i.e., relatively low energy_ X-rays
. Distance lends some safety
. The X-rays
and most UV are absorbed by a couple of feet of air. Any kind of eyeglasses, even those with nothing but windowpane glass in them, will also block
out the UV. Increasingly, opticians are recommending lightly tinted eyeglasses for persons who work all day at computer terminals.
C) Black Light/Plant Lights - The “Black Light” is the popular term used to describe ultra-violet energy in the 3200-4000A band. This invisible energy causes some materials Inks, dyes special paints and chemicals to glow. The phenomenon is useful for various laboratory studies, for mining and mineral exploration, and for industrial inspection and production. Although relatively inefficient for lighting, black light has found considerable architectural application for decorative effects.
Black light ( /BL) lamps are commonly used in “bug
Zappers”, they produce a long wavelength UVA radiation in the range of 350 to 400 nanometers. Visible energy in the 400 to 420 nanometer range is also emitted, giving the lamps a strong blue color when operated.
Black light Blue ( /BLB) lamps emit UVA radiation similar to BL lamps but are manufactured using a “black” glass that blocks most visible radiation. These lamps are often used decoratively, in disco lighting and theatrical production.
Diazo Reprographic Lamps The diazo lamp emits a blue light, peaking at approximately 417 nanometers, and is used primarily in rephographic equipment that employs the diazo process.
(G.E Spectrum, p.4-23)
The Treated Surface: since the eye is insensitive to “black light” UV-A radiation energy (from the lamp), the impression of brightness and color depends on the placement of fluorescent
chemicals for conversion. In effect
, these fluorescent
paints, dyes, and other coatings perform a function similar to the phosphor coating of a fluorescent
lamp. Treated surfaces become “area sources”, converting invisible energy into the longer wavelengths of visible light.
Efficiency: Black Light Paints, Dye, Lacquers, Water Colors:
Red...2%, Orange...4%, Yellow....8%, Green....7%, Blue....2%
Filters: Visible light reduces contrast and reduces the effectiveness of a black light installation. Therefore, the ambient light level
should be low, and any visible energy emitted by the source should be intercepted and absorbed by a special red-purple or dark blue filter. This filter may be attached to the fixture
as a cover
plate, or it may be integral with the lamp (dark glass bulbs).
Fluorens=one milliwatt of energy between 3200 and 4000 angstrom
Black Light Lamps: Filament
lamps are inherently weak and inefficient sources of ultra-violet. In addition, large quantities of visible and infra-red energy must be intercepted, and the dark bulb
(which acts as a filter) becomes very hot due to absorption. This extreme bulb
heat means that the lamp can be operated only intermittently, and periodic bulb
cooling is required (5 min. On, 10 min. Off.) Beam Control: Filament
lamps offer inherent advantages when used in precise reflectors. But, in this case, their use is limited due to inefficiency and bulb
heat. Principal lamp use is in supplementary units for close-range examination and inspection. 50 hours of life, at 250 watts puts out 470 fluorens. Advantages: no ballast
required. Low cost, and light weight fixtures, and full output immediately.
Black Light Lamps: special fluorescent
phosphors produce the 3,200-4,000 A. Band. These lamps are highly efficient sources of black light energy. Lamps can be obtained either unfiltered, or with self filtering bulbs. Beam Control: these lamps are used in trough-type reflectors which provide good brightness distribution on elongated surfaces (walls, etc
.) However, reflector
control of fluorescent
lamps is limited. The beam pattern
will be somewhat diffused, and perhaps more significant, the projection distance is limited. Advantages: most efficient source, Little visible light to be filtered, cool operating linear source, full output immediately, 40 watt
lamp can be dimmed or flashed. Dark filter bulbs reduce fluoren output to approximately 85% of unfiltered output. Approximate maintenance factor 0.50.
Do not use these lamps for diagnostic or therapeutic purposes.
Mercury Black Light Lamps: Mercury lamps are compact high output sources, offering advantages where accuracy of control is important. In some cases these lamps include integral filters and reflectors. Beam Control: the mercury arc provides a high output concentration of energy in a relatively small source. With proper reflector
design, then, the source is adaptable to give controlled beam patterns which can be projected substantial distances.
Advantages: compact source, efficient high output, available with integral reflectors approximate maintenance factor 0.60. one G.E brand name is Gold Lamps
Plant lights use both PL and PL/AQ phosphors were developed for use in horticultural and aquarium applications. The unique phosphor blend is designed to promote plant growth and enhance the appearance of plant and aquatic life.
Germicidal lights are clear
lamps made of a UV transmitting glass which transmits the 253.7 nanometer radiation from the mercury discharge - a wavelength effective in killing various forms of bacteria. Applications include water and air purification. Caution: these lamps emit short wavelength radiation. Be sure eyes and skin are properly protected at all times.
Diazo = UV Radiation measured perpendicular to lamp axis at 1m. distance with a relative spectral sensitivity according to IEC
. (See UV), Diazo falls between 320 and 440 nm. and includes some harmful UV-B and UV-C range. Measured as: irrad at 0hr µW/cm Square.
UV Radiation Breakdowns:
Bactericidal (germicidal): 220-300nm
Erythemal (skin reddening): 280-320nm
“Black Light”: 320-400nm
Note: True Black light lamps are different than Black Light Blue lamps which are common for use in lighting effects, and produce a visible change to surface colors, as opposed to true black light which produces an almost in-perceivable effect
on surfaces by the human eye, except with special phosphor paints and materials.