The Luminescence of Black Light
Black Light. What is it? It is a portion of the Ultra-Violet Spectrum that is
invisible to our eyes. We can
not distinguish it. However, when this radiation impinges on certain materials visible
light is emitted and this is
known as "fluorescence." Fluorescence is visible to the human eye, in that it makes an
object appear to "glow in
the dark."
There are several sources of ultra-violet light. These sources are: the sun, carbon
arcs, mercury arcs, and black
lights. In most cases, the production of ultra-violet light creates a reasonable amount
of heat.
Many materials exhibit the peculiar characteristic of giving off light or radiant energy
when ultra-violet light is
allowed to fall upon them. This is called luminescence. In most cases, the wave length
of the light radiated is longer
than that of the ultra-violet excitation but a few exceptions have been found.
The quantum theory attempts to explain this property by contending that a certain
outside excitation
causes an electron to jump from one orbit to another. It is then in an unstable
environment causing it to fall back into
its original orbit. This process releases energy, and if it is in the visible part of
the spectrum, we have a transient
light phenomenon. Ultra-violet light is an exciting agent which causes luminescence to
occur.
There are many materials which exhibit fluorescent characteristics. Many of which are
even organic. Teeth,
eyes, some portions of the skin, and even blood exhibit fluorescent qualities. Naturally
occurring minerals such as:
agate, calcite, chalcedony, curtisite, fluorite, gypsum, hackmanite, halite, opal
scheelite, and willemite, also have
similar characteristics. These materials can be used in industries.
The radiance of ultraviolet light is measured in units called "Angstrom." The intensity
of ultraviolet fluorescence
is the greatest between the 5000 and 6000 range. This being the range between the green
and yellow hues.
Ultra violet light is not readily visible. It is not visible because certain materials
reflect it. Ultra-violet light is
made visible due to the fact that it causes a reaction at the atomic level. When it
strikes the atom, some of the
electrons are sent into other orbits. This then creates an unstable situation which
causes the electron to fall back
into its place. This process produces energy, and this is what is seen. This discharge
of energy is what creates the
"glow" that is seen. I had no idea that light could cause such an strong reaction on
something. That something
being an atom is even more profound. Ultraviolet light causes the atom to lose a
subatomic particle then regain it,
and give off energy in the form of visible light. This is just amazing.
|