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Q:
How Does a black light work and what happens when a black light reacts to a glow in the dark material or reactive object?
I have a Sci-fair project on this and I do not fully understand the consepts of all this so would you breifly expain how this works , thank you 1
- Krista (age 13)
Red Deer Lake, Canada
A:
Krista-
Black lights give off ultraviolet rays. These are a type of light
that we can't see because the frequency is outside the range that our
eyes respond to. The Sun also gives off ultraviolet light, but mixed
with visible light.
Fluorescent materials (the ones that glow under a black light)
absorb the radiation from uv light and re-emit it in the spectrum of
colors that we can see. Some of the energy of each ray gets left in the
fluorescent material.
Some materials (the glow-in-the-dark ones) have a special type
of fluorescence called phosphorescence. The light energy can stay
trapped in them for a long time (minutes or longer) before leaking back
out, so you can see them glow even when no uv or other light still
shines on them.
Obviously, we haven't gone far into explaining any of this, but we hope we've got you started seeing a way to picture it.
Kim and Mike W
(published on 10/22/2007)
Follow-up on this answer.
