FREE ESSAY ON ELECTRO-MAGNETIC RADIATION

ELECTRO-MAGNETIC RADIATION

Electromagnetic Radiation
Electromagnetic radiation is defined as "the 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.
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 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. It's 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. 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.
Bibliography
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.