Under normal conditions, an atomic excitation lasts about 10-8 seconds. If an object emits visible light when lit up by ultraviolet light, it is fluorescent. If an object glows in the dark, after being in the light, it is phosphorescent.
| Under normal conditions, an atomic excitation lasts about 10-8 seconds. If an object emits visible light when lit up by ultraviolet light, it is fluorescent. If an object glows in the dark, after being in the light, it is phosphorescent. |
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 X-rays are produced by bombarding a metal target with electrons of several thousand eV kinetic energy. |
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Green laser pointers use Diode
Pumped Solid State Frequency Doubling technology. They begin
with a high power infrared laser diode that generates light at
808nm, which pumps a crystal of Nd:YVO4 (Neodymium-doped
Yttrium OrthoVanadate). That crystal generates light via
stimulated emission, at 1064 nm, which feeds a KTP (Potassium
Titanyl Phosphate, KTiOPO4) intracavity frequency doubler,
which produces a green beam at 532 nm. The green beam then
travels thru an output coupler, an expanding lens, an IR
filter to remove unwanted IR from the beam, then thru a
collimating lens and finally exits thru a glass output window.
The IR filter is needed to elminate the intense infrared light
that gets through the system, which is dangerous since it is
invisible to the eye. The green beam itself is also very, very
dangerous to the eye.
 Ordinary LED |
 FREQUENCY DOUBLING |
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 For an incandescent object, power output goes like the 4th power of the surface temperature and the peak output frequency is proportional to the temperature (in K). |