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PHYSICS:
BASIC PHYSICS: RADIATION:
ELECTROMAGNETIC RADIATION |
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Physics Brief: |
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Electromagnetic radiation is a
combination of oscillating
electric and
magnetic fields propagating through space and carrying energy
from one location to another. Generally,
electromagnetic radiation is classified by
wavelength and
frequency into
radio,
microwave,
infrared,
visible
light,
ultraviolet,
X-rays and
gamma rays.
When any wire (or other conducting object) conducts an alternating
current,
electromagnetic
radiation
is propagated at the same
frequency as the electric current. Depending on the
circumstances, it may behave as waves or as particles. As a wave,
it is characterized by a velocity (c),
wavelength, and
frequency. When considered as particles, they are known as
photons, and each has an energy related to the
frequency of the wave given by Planck's Relation.
The effects of
electromagnetic
radiation
depend on the amount of energy per quantum it carries. High
energies correspond to high
frequencies and short
wavelengths, and low energies correspond to low
frequencies and long
wavelengths. When
electromagnetic
radiation
passes through a conductor it induces an electric current flow in
the conductor; this effect is used in old-style
radio
communications. However, the induced current can also cause a
severe electric shock and either overload or destroy electrical
equipment. A strong
electromagnetic field can also cause cause electric currents
to flow across an air gap to ground, causing sparks that can start
a fire or cause an explosion. The oscillating
electrons of a
radio
transmitter can cause the antenna to heat up, creating the
potential for severe burns from RF energy. Even without direct
contact with equipment,
electromagnetic
radiation
may also cause certain molecules at a distance to oscillate and
thus heat up. These
electromagnetic
radiation
are known as RADHAZ or EMR hazards.
Much information about the physical properties of an object can be
obtained from its
electromagnetic spectrum; this can be either the spectrum of
light emitted from, or transmitted through the object. This
involves spectroscopy and is widely used in astrophysics. |
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