Electromagnetic Radiation Electromagnetic radiation is defined as
emission and transmission of energy in the form of electromagnetic waves"
(Chang, pp. 246). An electromagnetic wave consists of two waves at perpendicular
planes, on representing the electrical field while the other represents the
magnetic field. This spectrum is split up into about 81 octaves, much like the
octaves of sound, which scientists have categorized in order to depict the
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).
That, however, is at this point in time negligible because we either cannot
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
30 cm and a frequency of 30 kHz to 3,000,000 kHz. The waves are used in the
transmission of radio and television signals. AM and FM radio signals fall in
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.
The next slightly more energetic and shorter wavelength is microwaves.
Obviously, most are familiar with microwaves since they are always being used to
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.
Itís 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 donít 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
form of. Not much UV can get through the ozone layer, but a little does, and our
polluting industrial revolution has caused our protective layer to break down
allowing more UV radiation in and larger health problems to the world. It has
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.
X-rays, once again, are also well known to the public through their modern
medical usage. They are very energetic in nature and extremely harmful to the
living bodies, especially in the reproductive sites. They can easily pass
through skin and reveal the underlying structure of animals. X-rays have been
known to also cause cancer and even mutations. Prolonged exposure leads to
radiation poisoning and certain death. Itís wavelengths range from 100-.1
angstroms with frequencies of just under 10^17 to 10^20 cycles per second. It
contains 10 octaves. Gamma rays are the newly discovered form of radiation that
is associated with space, and is given off in reactions concerning the nuclei of
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. Itís 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.
Field, George B. and Chaisson, Eric J, The Invisible Universe: Probing the
Frontiers of Astrophysics. Boston, Birkhauser, 1985. Asimov, Isaac, Adding a
Dimension. New York, Double Day, 1964.