sábado, 24 de julio de 2010


Electromagnetic radiation consists of waves of electric and magnetic energy moving together (i.e., radiating) through space at the speed of light.  Taken together, all forms of electromagnetic energy are referred to as the electromagnetic "spectrum."  Radio waves and microwaves emitted by transmitting antennas are one form of electromagnetic energy.  They are collectively referred to as "radiofrequency" or "RF" energy or radiation.  Note that the term "radiation" does not mean "radioactive."  Often, the terms "electromagnetic field" or "radiofrequency field" may be used to indicate the presence of electromagnetic or RF energy.
The RF waves emanating from an antenna are generated by the movement of electrical charges in the antenna.  Electromagnetic waves can be characterized by a wavelength and a frequency.  The wavelength is the distance covered by one complete cycle of the electromagnetic wave, while the frequency is the number of electromagnetic waves passing a given point in one second.  The frequency of an RF signal is usually expressed in terms of a unit called the "hertz" (abbreviated "Hz").  One Hz equals one cycle per second.  One megahertz ("MHz") equals one million cycles per second.
Different forms of electromagnetic energy are categorized by their wavelengths and frequencies.  The RF part of the electromagnetic spectrum is generally defined as that part of the spectrum where electromagnetic waves have frequencies in the range of about 3 kilohertz (3 kHz) to 300 gigahertz (300 GHz).  Microwaves are a specific category of radio waves that can be loosely defined as radiofrequency energy at frequencies ranging from about 1 GHz upward. (Back to Index)
"Ionization" is a process by which electrons are stripped from atoms and molecules.  This process can produce molecular changes that can lead to damage in biological tissue, including effects on DNA, the genetic material of living organisms.  This process requires interaction with high levels of electromagnetic energy.  Those types of electromagnetic radiation with enough energy to ionize biological material include X-radiation and gamma radiation.  Therefore, X-rays and gamma rays are examples of ionizing radiation.
The energy levels associated with RF and microwave radiation, on the other hand, are not great enough to cause the ionization of atoms and molecules, and RF energy is, therefore, is a type of non-ionizing radiation.  Other types of non-ionizing radiation include visible and infrared light.  Often the term "radiation" is used, colloquially, to imply that ionizing radiation (radioactivity), such as that associated with nuclear power plants, is present.  Ionizing radiation should not be confused with the lower-energy, non-ionizing radiation with respect to possible biological effects, since the mechanisms of action are quite different.
por Edgar Servita 18.856.338

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