- Focus on Physics

Glossary I

A form of camera tube in which a beam
of high-velocity electrons scans a photoemissive mosaic. It was
invented by Vladimir Zworykin in 1923, and used in electronic
TV broadcasting from 1939 until it was replaced by more advanced
Is an object’s tendency to resist changes
in its state of motion. Therefore if it is at rest or moving at
a constant velocity, it takes a force to overcome the objects
inertia. The measure of inertia is the objects mass.
An instrument that works on the principle
that two waves that coincide with the same phase will amplify
each other while two waves that have opposite phases will cancel
each other out. It can be used to determine the wavelength of
light, measurement of the diameter of stars and many other uses.
An electrically charged molecule or atom
is known as an ion because it has gained or lost electrons from
its normal complement, a process known as ionization.
Ion Engine
Is a type of spacecraft propulsion that
uses beams of ions for propulsion, accelerated by passing them
through highly-charged grids (similar in concept to a vacuum tube).
This acceleration is very efficient, and ion thrusters can deliver
performance several orders of magnitude greater than traditional
rocket engines. [more]
Is the part of the atmosphere that is
ionized by solar radiation, and too tenuous to be cooled by contact
with other air. It forms the inner edge of the magnetosphere and
has practical importance because it reflects radio waves to distant
places on Earth.
Isotopes of a chemical
element are atoms whose nuclei have the same atomic number, Z,
but different atomic weights, A. The word isotope meaning at the
same place, is due to the fact that isotopes are located at the
same place on the periodic table.
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