Spectrum of electromagnetic waves

The spectrum of electromagnetic waves, showing the relationship between wavelength, frequency, and energy... 

Figure 32.1 The spectrum of electromagnetic waves, showing the relationship between wavelength, frequency, and energy. (Modified from Kiefer, J. 1990. Biological Radiation Effects. Springer-Verlag, Berlin. 444 pp.)...

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. 

Virtually all parts of the spectrum of electromagnetic radiation, from x rays to radio waves, have some practical application for the study of organic molecules. The use of x-ray diffraction for determination of the structures of... 

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.

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.

In the IR region of the spectrum, most modern instruments do not disperse the spectrum at all, although this was common with older instruments. Instead, an interferometer is used, and the constructive and destructive interference of electromagnetic waves is used to obtain spectral information through a technique called Fourier transformation. These IR instruments are further discussed in Feature 25-7 and in Section 26C-2. 

Wavelength Denomination A, measure for the length of a periodical oscillation of electromagnetic waves (see electromagnetic spectrum), unit nm (nanometer). 

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