ABSTRACT
Much has been learned since this handbook’s 3rd edition, but a full understanding of biological effects of electromagnetic fields is still to be achieved. The broad range of disciplines that must be studied has to be a factor in the apparent slow progress toward this ultimate end. Understanding how electric and magnetic fields can affect biological systems requires understanding of disciplines that include basic biology, medical science and clinical practice, biological and electrical engineering, basic chemistry and biochemistry, and fundamental physics and biophysics. The subject matter ranges over characteristic lengths and timescales, at one extreme with static fields and low frequencies with wavelengths of tens of kilometers to other extreme with sub-millimeter wavelength fields with periods below 10−12 s. Biological systems have response times that range from 10−15 s for electronic state transitions in molecules or atoms to many years for generations for humans and other organisms. This chapter is intended to provide a basic review of electric and magnetic fields and the relations between these fields and to define the terms used throughout the rest of these volumes. Maxwell’s equations defining these relations have been known for 2a long time, however, the solutions to these equations are often complex, as the biological materials can be inhomogeneous, nonlinear, time varying and anisotropic. Additionally, the geometric shapes involved may not lead to simple descriptions. Therefore, a number of approximations which depend on the ratio of the wavelength of the electromagnetic waves to the dimensions of the body being exposed are presented that simplify the calculations of the field strengths at a given location.
