Re: What colors are refracted from halogen light,fluorescent light, blacklight

The short answer to your question is that no matter what the light source,
all colors can be refracted. I say "can be" because refraction won't occur
unless the light passes through media of different densities. If a diver is
shining her flashlight at a fish, the flashlight beam won't exhibit
noticeable refraction because the medium that the light is passing through
(water) has pretty much the same density everywhere. But if a person
standing on the deck of a ship shines a flashlight at either the fish, or
the diver, the beam of the flashlight will be bent as it passes from the
air into the water,unless the flashlight is beam is perpendicular to the
water. The angle of bending (or refraction) has to do with the relative
densities of the two media.

Isaac Newton did a famous experiment with refraction. He found that if you
pass a beam of white light through a crystal prism, different colors of
light will be refracted by different amounts. The red light will be bent
less than the blue light. So white light goes into the prism, but rainbow
colors (a spectrum) come out. This effect is known as dispersion and it's
the basis of the whole science of spectroscopy, or the study of spectra.

Now, you originally asked about halogen lights, fluorescent lights, and
blacklights. To answer this completely, it's helpful if you know how these
lights work. 

Halogen lights work like the regular incandescent lights that you see
around the house. If you look inside a non-frosted incandescent lightbulb
(try it, it's interesting), you'll be able to see two wires with a tiny
filament hung between them. Electricity goes through these wires (which are
conductors and let electrons flow freely) and through the filament (which
nowadays is usually made of a metal called tungsten). The tungsten filament
is a resistor, which means the electricity has a tough time getting
through. This resistance causes the filament to heat up. It then releases
light, or optical radiation and heat, or infrared radiation. 

Halogen lights are the same as incandescent lights except the former kind
has a mixture of gas inside the bulb, while the latter has only vacuum. The
mixture of gas increases the efficiency, and the lifetime of the bulb. It
also makes for a hotter filament, which translates into a brighter light
source. 

Halogen lightbulbs emit all the colors that incandescent lighbulbs do, just
in different proportions. So if you had either kind of flashlight, it would
exhibit the same refraction and dispersion effects that I described above. 
Realize that the "beam" part of the setup is very important to wether you
see these effects. You won't see them by just staring at a naked bulb. The
light from your source has to be made into a beam (collimated) either by a
parabolic mirror, as in flashlights and car headlights, or by passing the
light through some kind of slit. 

Now, fluorescent lights and blacklights work in a different way. The
ancestor to both of these types of light is the mercury arc lamp. If you
take a glass bulb, fill it with mercury vapor, stick a mercury rod at
either end and run a current through the rods, the electricity will "arc"
frome one mercury rod to the other. You'll be able to see the spark.
However, these kinds of lamps emit most of their energy as ultraviolet (UV)
light, which is invisble to our eyes. But if you coat the inside of the
lamp with a fluorescent material, that coating will absorb the UV light and
then reradiate it as visible light. However, it's kind of difficult to
focus fluorescent light into a beam, so it would be hard to get the
diffracton effects I described earlier just because of the characteristics
of the bulb itself.

I'm not 100% sure about blacklights, but I think they're just a fluorescent
bulb with a different kind of coating. Blacklights look violet when they're
turned on, so they're probably radiating most of their light at blue and
violet wavelengths, with a healthy (or possibly unhealthy, if you spend all
your time under blacklights) portion of UV light as well. Invisible UV
light can also be refracted, but again, the nature of the bulb would make
ths difficult to achieve.

I had fun answering this question. Thanks for asking.