Electromagnetic Radiation Electromagnetic radiation is defined as ?the
(Chang, pp. 246). An electromagnetic wave consists of two waves at perpendicular
usefulness of the different properties. Theoretically electromagnetic waves can
be as long as the expansive width of the universe in one wave, to a wavelength
the size of a quanta (the smallest amount of energy that can be transmitted).
detect wavelengths so extremely large or infinitesimally small. So generally the
spectrum is regarded to be set between 30,000,000 km and .0001 angstroms (1 km
is equal to 1 X 10^13 angstroms). The longest and least energetic of the
accepted wavelengths are radio waves. Their wavelengths range from 300,000 km to
the long-wave radio range, while TV signals use the short-wave radio range,
somewhere in the 3 m wavelength. Radio waves take up about 30 of the 81 octaves.
cook food, but microwaves are also used in radiotelescopes and radar, even the
radiation from a neutral hydrogen atom falls in this range. Microwave range
extends from wavelengths of 30 cm to .3 cm and frequencies of 1-100 billion
cycles per second. This corresponds to 6 1/2 octaves. Then comes the infrared
range. While much of the radio spectrum passes easily through our atmosphere,
infrared is almost completely blocked off due to absorption by gaseous molecules
that reside there. Infrared waves are present during the transmission of heat.
It?s wavelengths range from .3 cm to .000076 cm with frequencies from 100
billion (10^11) to almost 10^14 cycles per second. 12 octaves are part of the
infrared spectrum. The visible spectrum with its single octave is the part of
the spectrum that only the blind are denied. The atmosphere is highly
transparent to the visible spectrum, and is one reason why biologists believe it
is the only part of the spectrum our eyes are sensitive to. Our sun produces
intense amounts of visible light, which also explains why we don?t perceive
the much less abundant radio wavelengths that are also impervious to our
atmosphere. The visible wavelengths range from .76 microns (7600 angstroms) to
.38 microns (3800 angstroms) with frequencies of slightly less than a
quadrillion (10^15). Many recognize UV or ultraviolet radiation because of
modern societies obsession with tanning, and the cancerous growths that may
follow. UV radiation is very energetic compared to the previous categories
discussed and will burn with the prolonged exposure, which tanning is a mild
polluting industrial revolution has caused our protective layer to break down
wavelengths from 3800-100 angstroms, with frequencies from a quadrillion (10^15)
to slightly less than 100 quadrillion (10^17). UV occupies about 5 octaves.
through skin and reveal the underlying structure of animals. X-rays have been
radiation poisoning and certain death. It?s wavelengths range from 100-.1
angstroms with frequencies of just under 10^17 to 10^20 cycles per second. It
atoms. These are the most energetic and shortest wavelengths that are very, very
lethal. They are often called cosmic rays and so far have no practical use other
than extraterrestrial observation. It?s frequencies are 100 quintillion
(10^20) and higher with wavelengths than 1/10th of an angstrom. Although
scientists have established these arbitrary borders for the electromagnetic
spectrum, there is truly no difference between them. Their only differences lie
in the amount of energy they contain, their wavelengths, and their frequencies.
They all behave as waves and particles, and all travel at the unerring speed of
light, 300,000 Km per second.
Frontiers of Astrophysics. Boston, Birkhauser, 1985. Asimov, Isaac, Adding a
Dimension. New York, Double Day, 1964.