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How is radiofrequency energy used?
Probably the most important use of RF energy is for telecommunications. Radio and TV
broadcasting, wireless phones, pagers, cordless phones, police and fire department radios,
point-to-point links and satellite communications all rely on RF energy.
Other uses of RF energy include microwave ovens, radar, industrial heaters and sealers, and
medical treatments. RF energy, especially at microwave frequencies, can heat water. Since
most food has a high water content, microwaves can cook food quickly. Radar relies on RF
energy to track cars and airplanes as well as for military applications. Industrial heaters and
sealers use RF energy to mold plastic materials, glue wood products, seal leather items such
as shoes and pocketbooks, and process food. Medical uses of RF energy include pacemaker
monitoring and programming.
How is radiofrequency radiation measured?
RF waves and RF fields have both electrical and magnetic components. It is often convenient
to express the strength of the RF field in terms of each component. For example, the unit
"volts per meter" (V/m) is used to measure the electric field strength, and the unit "amperes
per meter" (A/m) is used to express the magnetic field strength. Another common way to
characterize an RF field is by means of the power density. Power density is defined as power
per unit area. For example, power density can be expressed in terms of milliwatts (one
thousandth of a watt) per square centimeter (mW/cm2 or microwatts (one millionth of a
watt) per square centimeter (µW/cm2).
The quantity used to measure how much RF energy is actually absorbed by the body is called
the Specific Absorption Rate or SAR. The SAR is a measure of the rate of absorption of RF
energy. It is usually expressed in units of watts per kilogram (W/kg) or milliwatts per
gram (mW/g).
What biological effects can be caused by RF energy?
The biological effects of radiofrequency energy should not be confused with the effects from
other types of electromagnetic energy.
Section 5A: Safety
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