Electromagnetic radiation refers to waves of electric and magnetic energy moving together (i.e., radiating) through space as illustrated in Figure 1. When we talk about electromagnetic fields (EMF) or electromagnetic radiation (EMR), we are referring to the presence of electromagnetic energy at a particular location. Electromagnetic energy, like all waves, can be characterized by a wavelength and a frequency. The wavelength (λ) is the distance covered by one complete electromagnetic wave cycle, as shown in Figure 1. The frequency is the number of electromagnetic waves passing a given point in one second. For example, a typical radio wave transmitted by an FM radio station has a wavelength of about three (3) meters and a frequency of about 100 million cycles (waves) per second or “100 MHz.” One “hertz” (abbreviated “Hz”) equals one cycle per second. Therefore, in this case, about 100 million RF electromagnetic waves would be transmitted to a given point every second.
The electromagnetic “spectrum” (Figure 2) includes all the various forms of electromagnetic energy from extremely low frequency energy, with very long wavelengths, to X-rays and gamma rays, which have very high frequencies and correspondingly short wavelengths. In between these extremes are radio waves, microwaves, infrared radiation, visible light, and ultraviolet radiation, in that order. 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 to 300 gigahertz.
One kilohertz (kHz) equals one thousand hertz, one megahertz (MHz) equals one million hertz, and one gigahertz (GHz) equals one billion hertz. Thus, when you tune your FM radio to 101.5, it means that your radio is receiving signals from a radio station emitting radio waves at a frequency of 101.5 million cycles (waves) per second, or 101.5 MHz.
Probably the most important use for RF energy is in providing telecommunications services to the public, industry and government. Radio and television broadcasting, cellular telephones, pagers, cordless telephones, Wi-Fi, microwave point-to-point radio links and satellite communications are just a few of the many applications of RF energy for telecommunications. Microwave ovens and radar are examples of non-communications uses of RF energy.
An important fact to understand about electromagnetic fields is that they weaken quickly with distance from the source. Therefore, it is difficult to make assumptions about the actual strength of fields without measuring them. This is the reason why we conduct comprehensive EMF audits using sensitive meters that provide accurate results.
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