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The Epic Interactive Encyclopedia 1998
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Epic Interactive Encyclopedia, The - 1998 Edition (1998)(Epic Marketing).iso
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Interferometer
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1992-09-02
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In physics, a device that splits a beam of
light into two parts, the parts being
recombined after travelling different paths
to form an interference pattern of light and
dark bands. Interferometers are used in many
branches of science and industry where
accurate measurements of distances and angles
are needed. In the Michelson interferometer,
a light beam is split into two by a
semi-silvered mirror. The two beams are then
reflected off fully silvered mirrors and
recombined. The pattern of dark and light
bands is sensitive to small alterations in
the placing of the mirrors, so the
interferometer can detect changes in their
position to within one ten-millionth of a
metre. Using lasers, compact devices of this
kind can be built to measure distances, for
example to check the accuracy of machine
tools. In radio astronomy, interferometers
consist of separate radio telescopes, each
observing the same distant object, such as a
galaxy, in the sky. The signal received by
each telescope is fed into a computer.
Because the telescopes are in different
places, the distance travelled by the signal
to reach each differs and the overall signal
is akin to the interference pattern in the
Michelson interferometer. Computer analysis
of the overall signal can build up a detailed
picture of the source of the radio waves. In
space technology, interferometers are used in
radio and radar systems. These include
space-vehicle guidance systems, in which the
position of the spacecraft is determined by
combining the signals received by two
precisely spaced antennae mounted on it.