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Glossary Z

Zeeman Effect
Is the split of an spectral line into
several components in the presence of a magnetic field. In most
atoms, there exists several electronic configurations that have
the same energy, so that transitions between different pairs of
configurations correspond to a single line. Named after the Dutch
physicist Pieter Zeeman. [more]
Zener Diode
This device is especially designed so
as to have a greatly reduced breakdown voltage, the so-called
Zener voltage. A reverse-biased Zener diode will exhibit a controlled
breakdown and let the current flow to keep the voltage across
the Zener diode at the Zener voltage. For example, a 6.2 volt
Zener diode will exhibit a voltage drop of 6.2 volt if reverse
biased. However, the current is not unlimited, so the Zener diode
is typically used to generate a reference voltage for an amplifier
stage. [hyperphysics]
Zenith
Is the point in the sky where you are
looking when you look ‘straight up’ from the ground. More precisely,
it is the point on the sky with an altitude of +90 Degrees; it
is the pole of the horizontal coordinate system. Geometrically,
it is the point on the celestial sphere intersected by a line
drawn from the center of the Earth through your location on the
Earth’s surface.
Zero Point Energy
Is the energy in a system when the temperature
is reduced to absolute zero (0 Kelvin -2730 Celsius).
Zodical Light
Is composed of fine particles of dust in orbit around the
sun and is visible because of scattered sunlight from the
particles. The glow is brightest toward the sun from particles
with diameters between a couple of micrometers and a few
millimeters. From the mid-northern latitudes, the Zodiacal
light is most easily visible from a dark location under clear
and transparent skies just after evening twilight in the west
in February and March, and in the morning eastern sky, just
before the start of twilight in October. It is best seen at these
times because the plane of dust that comprises it lies in the
same plane as the ecliptic, and the ecliptic is at it’s steepest
angle to the horizon at these times of the year. [more]
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