Environmental Aspects of Microwave Radiation

Microwaves are electromagnetic waves which fail in the frequency range of approximately 30-300,000 MHz. The location of the microwave band in the electromagnetic spectrum is shown in Fig. 1. From the relation X = c/l), (where X is the wavelength of the radiation, c is the speed of light, and is the frequency) the range of the wavelength of the radiation in free space is determined to be 1000 centimeters-to 0.1 centimeter. Microwaves are often referred to as nonionizing radiation. Using the relationship, E = hp, (where h = Planck constant = 4.135 e.v.-sec) the energy per photon of the radiation can be calculated. For the microwave portion of the electromagnetic spectrum, the energy per photon ranges from 1.24 x 10-3 to 1.24 x 10-7 e.v. Since the ionization energy for atoms is of the order of 1 e.v., it can readily be seen that microwaves cannot ionize the atom. Therefore, any interaction between microwaves and biological material would be by a mechanism other than ionization. The best understood mechanism of interaction of microwave radiation and biological material is the absorption of the microwave energy with a resulting increase in temperature of the biological specimen. The amount of energy absorbed depends on the electrical properties of the specimen. The two electrical properties of importance are the dielectric