Radiant
Energy
All objects give off energy in the form of electromagnetic
radiation.
For instance, the heat that we feel from fire or the sun is
a form of electromagnetic radiation. Any object that has a temperature gives
off this form of energy which is infrared radiation. It does not require a medium to travel through;
it can travel through a vacuum. If an
object is heated to a high enough temperature, it will glow with visible light,
which is of higher energy than infrared radiation.
Objects that transmit low energy radiation will produce
electromagnetic radiation with long wavelengths and low frequencies. Objects that transmit radiation with a high
energy will produce waves with short wavelengths and high frequencies. The electromagnetic spectrum is shown below,
showing the relative wavelengths and frequencies for the different named types
of radiation.
(http://son.nasa.gov/tass/images/cont_emspec2.jpg)
Electromagnetic waves are essentially all alike, the only difference
being the wavelength. All electromagnetic
radiation consists of an electric field and a magnetic field which are at right
angles to each other.
(http://inms-ienm.nrc-cnrc.gc.ca/images/research_images/optical_comb/COMBFIG1.gif)
How
Are Electromagnetic Waves Produced?
(http://www.weather.nps.navy.mil/~psguest/EMEO_online/module2/module_2_3.html)
A charged particle, such as a proton or an electron produces
an electric field. This electric field
is either directed towards the negative particle or away from the positive
particle. The electric field is
multi-directional. When the electric
field consisting of a charged particle moves through a wire, such as in a circuit,
a magnetic field is produced at right angles to the electric field. The
magnetic field is “wrapped” around the wire.
This is the principle behind an electromagnet. Electric fields and magnetic fields influence
each other. If you move a magnet along a
wire, you influence the movement of charged particles and so produce an
electric field. Electromagnetic
radiation, which consists of both electric and magnetic components, is produced
when a charged particle accelerates. The
charge produces the electric component and the movement of the charge creates
the magnetic component. Since the
particle is accelerating, (moving faster, slower or changing direction), these
electric and magnetic fields are constantly in flux, they form and disappear
over and over. This pattern of repeated
formation of the fields is the origin of the wave propagation.