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.


X-rays are produced by bombarding a metal target with electrons of several thousand eV kinetic energy.

The incoming electrons have enough kinetic energy to knock electrons out of the innermost, most tightly bound levels of the atom. When these vacancies are filled, very energetic photons must therefore be emitted.

Looking at these “characteristic X-rays” from a sample of unknown material is the quickest way to determine specifically what types of atoms the material is composed of.


LASER = light amplification by stimulated emission of radiation.

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