ABSTRACT
All radiation is a form of energy with a wide electromagnetic spectrum. An electromagnetic œeld is associated with two components, the electric œeld and the magnetic œeld, that often work together to create an electromagnetic œeld. Electric œelds arise from differences in voltage: the higher the voltage, the greater the strength of the œeld. The strength of an electric œeld is measured in volts per meter (V/m). Magnetic œelds arise when the electric current £ows: the greater the current strength, the stronger the magnetic œeld. The strength of the magnetic œeld is measured in amperes per meter (A/m), but more commonly it is measured in microtesla (µT). The electromagnetic œeld is characterized by its frequency or its corresponding wavelength. Electromagnetic radiation can be grouped in two major classes: ionizing radiation and nonionizing radiation. Ionizing radiation has a higher frequency and shorter wavelength and enough energy to knock out one electron from one of the orbits of the atom. Nonionizing radiation has a lower frequency and higher wavelength and has enough energy to move atoms in a molecule around or cause them to vibrate, but not enough to remove an electron from one of the orbits of the atom. The electromagnetic œeld is present in the atmosphere and is generated by humans. Humanmade sources of electromagnetic radiation of the nonionizing radiation type include cell phones, microwave, and television and radio-transmitters. Radio frequencies are measured in watts per square meter (W/m2). The previous 10 chapters have discussed in detail various aspects of ionizing radiation.
