Environmental aspects of microwave radiation.

Properties of Microwaves 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 constant, a measure of the polarizability of the medium, and the conductivity, a measure of the ease in which electrically charged particles move through the medium. Since water has a relatively high dielectric constant and conductivity, the absorption of microwave energy is greater in biological materials FreqLv) Wave length(X) Energy Hertz Cm A E.V. Approx.