Electromagnetic waves properties

Altliough a complete treatment of optical phenomena generally requires a full quantum mechanical description of tire light field, many of tire devices of interest tliroughout optoelectronics can be described using tire wave properties of tire optical field. Several excellent treatments on tire quantum mechanical tlieory of tire electromagnetic field are listed in [9]. 

Thus, for electromagnetic radiation of frequency, V, the wavelength in vacuum is longer than in other media. Another unit used to describe the wave properties of electromagnetic radiation is the wavenumber, V, which is the reciprocal of wavelength... 

Two additional wave properties are power, P, and intensity, I, which give the flux of energy from a source of electromagnetic radiation. 

Each body having a temperate above absolute zero radiates energy in the form of electromagnetic waves. The amount of energy emitted is dependent on the temperature and on the emissivity of the material. The wavelength or frequency distribution (the spectrum) of the emitted radiation is dependent on the absolute temperature of the body and on the surface properties. 

Heinrich Hertz in 1887 who used an oscillating circuit of small dimensions to produce electromagnetic waves which had all of the properties of light waves... 

The sensor systems outlined in the present chapter use evanescent electromagnetic radiation to monitor various analytes in aqueous solutions. Therefore, as a beginning, the basic properties of evanescent electromagnetic waves and the so-called TIR phenomena are summarized. Afterwards, two types of waveguide modes will be briefly discussed guided and leaky modes, which both generate evanescent waves at a solid/liquid boundary. 

Prior to von Laue, physicists had obtained information about crystal structure through chemical analysis, interfacia] angle measurements, and the determination of physical properties. There was little knowledge of the internal structure, although it was believed that crystals were built up by periodic repetition of some unit, probably an atom or molecule, and that these units were about 1 or 2 A apart. It was also suspected, but not confirmed, that X-rays were electromagnetic waves of about 1 or 2 A in wavelength. 

D-glass with high dielectric properties, transparent to electromagnetic waves. The principal applications relate to the manufacture of radomes, electromagnetic windows and high-tech printed circuit boards. 

Refractive index or index of refraction is the ratio of wavelength or phase velocity of an electromagnetic wave in a vacuum to that in the substance. It measures the amount of refraction a ray of light undergoes as it passes through a refraction interface. Refractive index is a useful physical property to identify a pure compound. 

In addition to irradiance and frequency, a monochromatic (i.e., time-harmonic) electromagnetic wave has a property called its state of polarization, a property that was briefly touched on in Section 2.7, where it was shown that the reflectance of obliquely incident light depends on the polarization of the electric field. In fact, polarization would be an uninteresting property were it not for the fact that two waves with identical frequency and irradiance, but different polarization, can behave quite differently. Before we leave the subject of plane waves it is desirable to present polarization in a systematic way, which will prove to be useful when we discuss the polarization of scattered light. 

The notion of homogeneity is not absolute all substances are inhomogeneous upon sufficiently close inspection. Thus, the description of the interaction of an electromagnetic wave with any medium by means of a spatially uniform dielectric function is ultimately statistical, and its validity requires that the constituents—whatever their nature—be small compared with the wavelength. It is for this reason that the optical properties of media usually considered to be homogeneous—pure liquids, for example—are adequately described to first approximation by a dielectric function. There is no sharp distinction between such molecular media and those composed of small particles each of which contains sufficiently many molecules that they can be individually assigned a bulk dielectric function we may consider the particles to be giant molecules with polarizabilities determined by their composition and shape. 

Erma, V. A., 1969. Exact solution for the scattering of electromagnetic waves from bodies of arbitrary shape III. Obstacles with arbitrary electromagnetic properties, Phys. Rev., 179, 1238-1246. 

The accurate quantum mechanical first-principles description of all interactions within a transition-metal cluster represented as a collection of electrons and atomic nuclei is a prerequisite for understanding and predicting such properties. The standard semi-classical theory of the quantum mechanics of electrons and atomic nuclei interacting via electromagnetic waves, i.e., described by Maxwell electrodynamics, turns out to be the theory sufficient to describe all such interactions (21). In semi-classical theory, the motion of the elementary particles of chemistry, i.e., of electrons and nuclei, is described quantum mechanically, while their electromagnetic interactions are described by classical electric and magnetic fields, E and B, often represented in terms of the non-redundant four components of the 4-potential, namely the scalar potential and the vector potential A. 

A significant change in the theoretical treatment of atomic structure occurred in 1924 when Louis de Broglie proposed that an electron and other atomic particles simultaneously possess both wave and particle characteristics and that an atomic particle, such as an electron, has a wavelength X = h/p = h/mv. Shortly thereafter, C.J, Davisson and L.H. Germer showed experimentally the validity of this postulate. Dc Broglie s assumption that wave characteristics are inherent in every atomic particle was quickly followed by the development of quantum mechanics, in its most simple form, quantum mechanics introduces the physical laws associated with the wave properties of electromagnetic radiation into the physical description of a system of atomic particles. By means of quantum mechanics a much more satisfactory explanation of atomic structure can be developed. 

The modern point of view is that, for every particle that exists, there is a corresponding field with wave properties. In the development of this viewpoint, the particle aspects of electrons and nuclei were evident at the beginning and the field or wave aspects were found later (this was the development of quantum mechanics). In contrast, the wave aspects of the photon were understood first (this was the classical electromagnetic theory of Maxwell) and its particle aspects only discovered later, From this modern viewpoint, the photon is the particle corresponding to the electromagnetic field. It is a particle with zero rest mass and spin one. 

Einstein started this great development as early as 1905 by an almost unimaginable act of vision, when he concluded that the concept of such an electromagnetic wave does not suffice to explain important properties of light. He drew the revolutionary conclusion that there must exist light-particles, the photons, The particle-wave duality was born, Einstein recognized die fertility of his idea, but lie was never completely satisfied with the conceptual basis of quantum mechanics, The lack of complete causality and the frequent use of probability instead of certainty were always a matter of deep concern for him. 

There are numerous properties of materials which can be used as measures of composition, e.g. preferential adsorption of components (as in chromatography), absorption of electromagnetic waves (infra-red, ultra-violet, etc.), refractive index, pH, density, etc. In many cases, however, the property will not give a unique result if there are more than two components, e.g. there may be a number of different compositions of a particular ternary liquid mixture which will have the same refractive index or will exhibit the same infra-red radiation absorption characteristics. Other difficulties can make a particular physical property unsuitable as a measure of composition for a particular system, e.g. the dielectric constant cannot be used if water is present as the dielectric constant of water is very much greater than that of most other liquids. Instruments containing optical systems (e.g. refractometers) and/or electromechanical feedback systems (e.g. some infra-red analysers) can be sensitive to mechanical vibration. In cases where it is not practicable to measure composition directly, then indirect or inferential means of obtaining a measurement which itself is a function of composition may be employed (e.g. the use of boiling temperature in a distillation column as a measure of the liquid composition—see Section 7.3.1). 

In order to generate the second harmonic of an electromagnetic wave, one needs to make use of some device which has a non-linear property. In the case we are considering, the non-linear relationship made use of is that between applied electric field and electric polarisation. One can write... 

Radar techniques are based on the exploitation of three main properties of electromagnetic waves a) electromagnetic waves travel at the velocity of light so that the time interval between the transmission of a signal and its returning echo, divided by two and multiplied by the... 

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