Electromagnetic Radiation and Human Health
The macroscopic theory of the electromagnetic field is based on the following four vector quantities Based on empirical experience, it is reasonable to assume that these quantities are continuous and continuously differentiable almost everywhere in the computational domain, except for sets of zero measure such as interfaces separating materials with different electromagnetic properties. The points where the field is continuous are called regular, the others are singular. The electromagnetic field may be classified with respect to a number of various properties and characteristics, for example The mathematical model of the electromagnetic field, that nowadays is known as the Maxwell's equations, first appeared in the Treatise on Electricity and Magnetism by James Clerk Maxwell in 1873. These equations are assumed to be one of the greatest achievements of the 19th-century mathematics. Among Maxwell's other remarkable contributions were (a) the observation that light is an...
Many natural processes can be sufficiently well described on the macroscopic level, without taking into account the individual behavior of molecules, atoms, electrons, or other particles. The averaged quantities such as the deformation, density, velocity, pressure, temperature, concentration, or electromagnetic field are governed by partial differential equations (PDEs). These equations serve as a language for the formulation of many engineering and scientific problems. To give a few examples, PDEs are employed to predict and control the static and dynamic properties of constructions, flow of blood in human veins, flow of air past cars and airplanes, weather, thermal inhibition of tumors, heating and melting of metals, cleaning of air and water in urban facilities, burning of gas in vehicle engines, magnetic resonance imaging and computer tomography in medicine, and elsewhere. Most PDEs used in practice only contain the first and second partial derivatives (we call them second-order...
Section 7.1 presents important basic facts about the macroscopic (continuous) model of the electromagnetic field, such as the four basic laws of electromagnetics, the Maxwell's equations in the integral and differential forms, media characteristics, basic properties of conductors, dielectrics and magnetic materials, and interface conditions. With an appropriate insight, many typical problems of electromagnetics can be formulated in terms of potentials and solved by means of the standard continuous finite elements. The scalar electric potential and the scalar and vector magnetic potentials are introduced in Section 7.2. The equations for the field vectors and the time-harmonic Maxwell's equations are derived in Section 7.3.
This computation is rooted in the construction of electrostatic micromotors. These devices, which are capable of transforming the electric energy into motion analogously to standard electromotors, do not contain any coils or electric circuits that could be destroyed by strong electromagnetic waves. The goal of this computation is a highly-accurate approximation of the distribution of the electric field in a domain containing two electrodes and a thin object placed between them. The problem is plane-symmetric, and Figure B.20 shows one-half of the domain fi.
7.5.1 The electromagnetic spectrum Electromagnetic (EM) energy is all energy which travels in a periodic harmonic manner at the velocity of light. Electromagnetic energy is normally considered to consist of a continuum of wavelengths referred to as the EM spectrum (Figure 7.18). Figure 7.18 The electromagnetic spectrum
Electromagnetic Waves (EM) - Electromagnetic radiation is the propagation of energy through space by means of electric and magnetic fields that vary in time. Electromagnetic radiation may be specified in terms of frequency, vacuum wavelength, or photon energy. For water purification, EM waves up to the low end of the UV band will result in heating the water. (This includes infrared as well as most lasers.) In the visible range, some photochemical reactions such as dissociation and increased ionization may take place. At the higher frequencies, it
The idea of using ionizing radiation to disinfect water is not new. Ionizing radiations can be produced by various radioactive sources (radioisotopes), by X-ray and particle emissions from accelerators, and by high-energy electrons. The advances in reliable, relatively low-cost devices for producing high-energy electrons are more significant.