Spectrum of the electromagnetic wave

Figure 2.2. Top - the schematic of the transverse electromagnetic wave in which electric (E) and magnetic (H) vectors are mutually perpendicular, and both are perpendicular to the direction of the propagation vector of the wave, k. The wavelength, is the distance between the two neighboring wave crests. Bottom - the spectrum of the electromagnetic waves. The range of typical x-ray wavelengths is shaded. The boundaries between different types of electromagnetic waves are diffuse.

When radiation hits a body, some of it will be reflected, some absorbed and some transmitted. These portions are represented by the reflectivity r, the absorptivity a, and the transmissivity r. These three dimensionless quantities are not purely properties of the irradiated material, they also depend on the kind of radiation which strikes the body. Of main influence is the distribution of radiation over the wave length spectrum of the electromagnetic waves incident on the material. However it can always be said that... 

Radars and cordless telephones also use electromagnetic radiation in the microwave region. The wavelength of the electromagnetic waves used in radio and T V broadcasting usually ranges between 1 and 1000 m in the radio wave region of the spectrum. 

It has sometimes been stated that the new frontier for research in high frequency electronics lies in the Terahertz band, which falls between the microwave and infrared parts of the electromagnetic wave spectrum and includes the frequency interval 0.3xl0 < / < 10 xlO Hz [300 < /< 10,000 GHz or 0.3 < /< 10 THz], corresponding to wavelengths 1000 < /l< 30 micrometers, and energies 1.24 < < 41.3 meV. This regime... 

FIGURE 7.1 Thermal radiation a region of the electromagnetic-wave spectrum. 

Now we shall discuss some features of the electromagnetic wave spectrum in mixed crystalline solutions using the equations for the dielectric constant tensor of the solution derived in the mean polarizability approximation. We know that the effects of concentration broadening of absorption spectra are lost in this approximation. However, Onodera and Toyozawa (16), Dubovsky and Konobeev (17), Hoschen and Jortner (18), and Hong and Robinson (19), who have actually studied the corrections to the mean polarizability approximation, have shown that... 

If the light emitted by the neon is passed through a glass prism, neon s atomic emission spectrum is produced. The atomic emission spectrum of an element is the set of frequencies of the electromagnetic waves emitted by atoms of the element. Neon s atomic emission spectrum consists of several individual lines of color corresponding to the frequencies of the radiation emited by the atoms of neon. It is not a continuous range of colors, as in the visible spectrum of white light. 

Heat transfer by thermal radiation requires no intervening medium. Thermal radiation is the energy emitted by a body solely due to the temperature of the body and at a frequency that falls within a small portion of the electromagnetic wave spectrum as shown in Figure 7.9. 

The wave lengths of the various parts of the electromagnetic spectrum of immediate interest are ... 

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. 

One important feature of compound semiconductors is that their bands span a much wider range that of elemental silicon and can therefore cover a wider range of the electromagnetic spectrum, in particular the visible region. Compound semiconductors are also more often direct, i.e., there is conservation of the wave vector for optical transitions, leading to allowed... 

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