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Glossary U

Ultra Microscope
An instrument for viewing particles too small to be seen
by ordinary microscope. A narrow beam of light focused into
the liquid with a black background, the particles (less than
0.1 micron in diameter) are detected by scattering the light.
[Also see Tyndall Effect]
Ultrasonic
Are frequencies higher than humans can
hear, in excess of 20 K Hertz. These frequencies are used in Ultra
scan
during pregnancy to examine the baby’s development.
Ultraviolet (UV)
Radiation is electromagnetic radiation
of a wavelength shorter than that of visible light, but longer
than that of soft X-rays. The name means “beyond violet” (from
Latin ultra, “beyond”), violet being the color of the shortest
wavelength of visible light. UV itself can be subdivided into
near UV (380-200 nm wavelength) and extreme or vacuum UV (200-10
nm). [more]
Uncertainty Principle (Heisenberg’s Uncertainty Principle)
States that one cannot simultaneously know both the
position and the momentum of a given object to arbitrary precision.
It furthermore precisely quantifies the imprecision. It is one of
the cornerstones of quantum mechanics and was discovered
by Werner Heisenberg in 1927. [more]
Unified Field Theory
A theory that explains the four fundamental
forces of nature and brings together relativity and quantum
mechanics in one theory, sometimes called the Theory of
Everything (TOE). [more]
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