Electromagnetic Frequency Spectra

Many other interaction energies come from the electromagnetic frequency spectrum. They can come from outside of the ultraviolet, visible, and infrared frequency ranges. All that is required is an element of the model protein in water that is able to take up the energy. The dipole moment of the peptide group with its positive end at the NH and its negative end at the oxygen of the CO provides one site of inter-... 

FIGURE 22.5 Electromagnetic frequency spectrum (a) to light and beyond, (b) selected radio frequencies. Source-1996 Hammett Edison, Inc. With permission.)... 

Electromagnetic frequency spectrum and associated wavelengths. (From Fay, R, Introduction, in The RF and Microwave Handbook, Golio, M., Ed., CRC Press, Boca Raton, FE, 2001, p. 1-2.)... 

Nonionizing radiation registers at the low end of the electromagnetic frequency spectrum. It lacks the energy required to cause ionization but can cause molecules to vibrate. The health effects depend on the particular wavelength of the radiation involved. The types of nonionizing radiation include UV, infrared, laser, microwave, and low-frequency radiation. 

In spectroscopy one frequently deals with functions of time, f(t), such as the position r(t) of an electric charge, or a time-varying dipole moment, fi(t), which lead to emission of electromagnetic radiation if the second time derivative is not vanishing. The frequency spectrum of the associated emission is obtained by Fourier transform of the function of time. If the absolute value of the function, /(t), is integrable over all times, —co < t < co, one defines the Fourier transform according to... 

Electromagnetic radiation spectrum from the audible frequency up to that of the cosmic rays. 

Figure 2.5 The electromagnetic spectrum as a piano. Imagine some alien beast playing this immense electromagnetic keyboard. Illustrated here are 30 octaves of electromagnetic frequency in which the wavelength doubles with each octave. Visible light occupies only a part of one octave. Labels are only approximate. See figure 2.4 for more precise locations. [After Denis Postle, Fabric of the Universe (New York Crown, 1976), 59.]...

Van der Waals forces result from charge and electromagnetic-field fluctuations at all possible rates. We can frequency analyze these fluctuations over the entire frequency spectrum and integrate their force consequences over the frequency continuum. Alternatively, the modern theory shows a practical way to reduce integration over all frequencies into summation by the gathering of spectral information into a set of discrete sampling frequencies or eigenfrequencies. The nature and choice of the frequencies at which dielectric functions are evaluated reveal how the modern theory combines material properties with quantum mechanics and thermodynamics. 

Mathematical form of dependence on material properties, 43 Mathematical form of the charge-fluctuation free energy, 45 Frequencies at which e s, A s, and Rn s are evaluated, 46 About the frequency spectrum, 51 Retardation screening from the finite velocity of the electromagnetic signal, 51 Effective power law of van der Waals interaction versus separation, 55 Van der Waals pressure, 57 Asymmetric systems, 58... 

As described in earlier sections, any two material bodies will interact across an intermediate substance or space. This interaction is rooted in the electromagnetic fluctuations— spontaneous, transient electric and magnetic fields—that occur in material bodies as well as in vacuum cavities. The frequency spectrum of these fluctuations is uniquely related to the electromagnetic absorption spectrum, the natural resonance frequencies of the particular material. In principle, electrodynamic forces can be calculated from absorption spectra. 

Figure 1.3 Acoustic-wave spectrum. Almost as broad as the familiar electromagnetic-wave spectrum, the spectrum of acoustic waves that have been excited or detected covers frequencies that range over roughly eighteen orders of magnitude. The four sensors on which we concentrate, indicated by bold lines, range in operation frmn below 1 MHz to slightly above KXX) MHz.

Electromagnetic radiation in the microwave frequency spectrum is absorbed most strongly by molecules with permanent dipole moments (4). The relaxation phenomenon of this absorbed power manifests itself in a heatlike reaction. The University of Colorado Oil Shale Project has studied the degradation of the liquid-fuel precursor (kerogen) by micro-wave interaction. Kerogen is a moderately strong absorber of this radia-... 

Table 1 Frequency spectrum of the electromagnetic field radiation in the frequency range of 0-10 ° Hz. It includes some examples of broadly used applications and also shows the separation between nonionizing and ionizing radiation as a function of the frequency range...

Light near the middle of the ultraviolet region of the electromagnetic radiation spectrum has a frequency of 2.73 X s L Yellow light near the middle of the visible region of the spectrum has a frequency of 5.26 X 10 s L Calculate the wavelength that corresponds to each of these two frequencies of light. 

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... 

The sense of smell challenges chemical understanding. On the one hand, given the structure of a new molecule a chemist can predict its spectroscopic properties over a wide domain of electromagnetic frequencies. A mixture ordinarily displays a spectrum that superimposes the spectra of its individual components, unless they physically interact with each other. In the chemical senses, on the other hand, perceptions of mixtures often cannot be inferred from their constituents, even though the components do not interact at the molecular level. Moreover, no one can reliably predict the organoleptic properties (taste or smell) of a new molecule from its structure. Even if... 

Microwaves (0.3-300 GHz) lie between radiowave (RF) and infrared (IR) frequencies in the electromagnetic radiation spectrum. Microwaves can be reflected, absorbed and/or transmitted by materials. Microwaves can interact with materials through either polarization or conduction processes. Polarization involves the short-range displacement of charge through... 

Distant lightning return stroke fields are often referred to as sferics (called atmospherics in the older literature). The peak in the sferics frequency spectrum is near 5 kHz due to the bipolar or ringing nature of the distant return-stroke electromagnetic signal and to the effects of propagation. 

IR spectroscopy is one of the most powerful spectroscopic tools available for the analysis of polymer systems (a.l). IR spectroscopy is molecularly specific with high sensitivity. It is based on the absorption or attenuation by matter of electromagnetic radiation of a specified motion of chemical bonds. Through quantum physics, nature defines the absorption modes, their locations in the frequency spectrum and the amount of energy absorbed by each molecule. The absorbance at a characteristic frequency is a measure of the concentration of the chemical species being probed in the sample. 

For polarized measurements the relationship between refractive index and absorbance is critical. Directional absorbance changes lead to birefringence, which in turn will affect strongly the nature of polarized light. The Kramers-Rronig relations come into play for cases like this one (15). They relate the complete electromagnetic absorption spectrum of a material to its refractive index at all frequencies and vice versa. A form of the relation is... 

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