The
electromagnetic spectrum includes
gamma rays, X-rays, ultraviolet,
visible, infrared, microwaves,
and radio waves. The only difference
between these different types
of radiation is their wavelength
or frequency. Wavelength increases
and frequency (as well as energy
and temperature) decreases from
gamma rays to radio waves. All
of these forms of radiation travel
at the speed of light (186,000
miles or 300,000,000 meters per
second in a vacuum). In addition
to visible light, radio, some
infrared and a very small amount
of ultraviolet radiation also
reaches the Earth's surface from
space. Fortunately for us, our
atmosphere blocks out the rest,
much of which is very hazardous,
if not deadly, for life on Earth.
Infrared radiation lies between
the visible and microwave portions
of the electromagnetic spectrum.
Infrared waves have wavelengths
longer than visible and shorter
than microwaves, and have frequencies
which are lower than visible and
higher than microwaves. Infrared
is broken into three categories:
near,
mid and far-infrared. Near-infrared
refers to the part of the infrared
spectrum that is closest to visible
light and far-infrared refers
to the part that is closer to
the microwave region. Mid-infrared
is the region between these two.
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