palmOne Vision Smart Device Treo 650 User Manual page 287

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.
Very high levels of electromagnetic energy, such as is found in X-rays and gamma rays can ionize
biological tissues. Ionization is a process where electrons are stripped away from their normal
locations in atoms and molecules. It can permanently damage biological tissues including DNA,
the genetic material. Ionization only occurs with very high levels of electromagnetic energy
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