Wireless LANs are used at airports, by local police and other public service organizations, and in hospitals for nurses and doctors to enter or obtain data at the patient's bedside. Television, whose signals are also transmitted by radio frequency energy, has been with us for nearly 50 years. The radio frequency range, including microwaves, has many other uses in communication including police, fire, amateur, and Citizens' band radio, marine radios, AM and FM radio, UHF television, and traffic and weather radars. More recently, different radio frequencies have been used for telephones, paging and other personal communication systems. The term radiation simply means that something can spread out from its source, as heat can radiate from a campfire.
Radio waves are a type of energy that radiates out from a source, just as light or sound does.
The radio frequency energy produced by most sources are transmitted by antennas over distance. Radio waves are quite different from ionizing or nuclear radiation. As the figure shows, the spectrum of electromagnetic energies includes two categories, non- ionizing and ionizing radiation. The non-ionizing frequencies are those that produce energy that cannot break chemical bonds, or ionize, the chemicals in living tissue. Ionizing radiations, which include X- and gamma rays are the highest frequencies in the spectrum.