Portion of the Electromagnetic Spectrum

Celsius. The energy distribution of the radiation emitted by this surface is fairly close to that of a classical black body (i.e., a perfect emitter of radiation) at a temperature of 5,500°C, with much of the energy radiated in the visible portion of the electromagnetic spectrum. Energy is also emitted in the infrared, ultraviolet and x-ray portions of the spectrum (Figure 1). 

In 1957, this team of brothers-in-law started working together on Townes s idea for an optical maser. They found atoms that they felt had the most potential, based on transitional probabilities and lifetimes. However, there was still one major problem In the visible light portion of the electromagnetic spectrum, atoms don t remain in an excited state as long as... 

C07-0007. A compact disc player uses light of frequency 3.85 X lO s to read the information on the disc, (a) What is this light s wavelength (b) In what portion of the electromagnetic spectrum (visible, ultraviolet, and so on) does this wavelength fall (c) What is the energy of one mole of photons at this frequency ... 

Many characteristic molecular vibrations occur at frequencies in the infrared portion of the electromagnetic spectrum. We routinely analyze polymers by measuring the infrared frequencies that are absorbed by these molecular vibrations. Given a suitable calibration method we can obtain both qualitative and quantitative information regarding copolymer composition from an infrared spectrum. We can often identify unknown polymers by comparing their infrared spectra with electronic libraries containing spectra of known materials. 

X rays comprise that portion of the electromagnetic spectrum which lies between ultraviolet and gamma rays. The range of wavelengths is typically from about 0.01 to 100 A. Because of their very short wavelengths, X rays are powerful probes of atomic structure. 

Fig. 1 A portion of the electromagnetic spectrum comparing infrared energy with other forms of radiation.

Red light has the longest wavelengths in the visible portion of the electromagnetic spectrum. Longer wavelengths are, therefore, beyond the red, which, from Latin is infrared. 

As mentioned above, the NIR portion of the electromagnetic spectrum is located between the visible and mid-range infrared sections, roughly 750-2500nm or 13,333-4000cm It mainly consists of overtones and... 

Ultraviolet Radiation The portion of the electromagnetic spectrum emitted by the sun adjacent to die violet end of die visible light range. Often called black light , it is invisible to the human eye but when it falls on certain surfaces it causes them to fluoresce or emit visible light responsible for the photo-oxidation of certain compounds including hydrocarbons. 

The interaction of electromagnetic radiation with matter in the domain ranging from the close ultraviolet to the close infrared, between 180 and 1,100 nm, has been extensively studied. This portion of the electromagnetic spectrum, called UV/Visible because it contains radiation that can be seen by the human eye, provides little structural information except the presence of unsaturation sites in molecules. However, it has great importance in quantitative analysis. Absorbance calculations for compounds absorbing radiation in the UV/Visible using Beer-Lambert s Law is the basis of the method known as colorimetry. This method is the workhorse in any analytical laboratory. It applies not only to compounds that possess absorption spectra in that spectral region, but to all compounds that lead to absorption measurements. 

Does visible light constitute a large or small portion of the electromagnetic spectrum ... 

The NMR transition frequency depends on the magnitude B of the applied magnetic field and has no significance unless B is specified. A magnetic field readily attainable is 10,000 gauss at this value of B, Eq. (8.23) gives the resonance frequency of a proton as 42.6 MHz. NMR transitions thus fall in the radio-frequency (rf) portion of the electromagnetic spectrum. NMR resonance frequencies in MHz for some nuclei at... 

The increase in A(J caused by tt bonding is substantial enough in many cases that the absorption maximum for the h -to-ejj electronic transition is blue-shifted out of the visible region into the ultraviolet portion of the electromagnetic spectrum, with the result that the complexes are colorless. This is the case for the metal carbonyls, for example. 

Astronomy. The potential of using the infrared portion of the electromagnetic spectrum for investigating celestial bodies and interstellar space has been considered by some astronomers for a number of years. This concept was first proposed by William Herschel. It has only been within the last few decades, however, that serious experiments in infrared astronomy have been made. 

MICROWAVE SPECTROSCOPY. A type of adsorption spectroscopy used in instrumental chemical analysis that involves use of that portion of the electromagnetic spectrum hav ing wavelengths in the range between the far infrared and the radiofrequencies, i.e.. between 1 nun and. 111 cm. Substances to be analyzed are usually in the gaseous state. Klystron tubes are used as microwave source. 

PHOTOMETRIC ANALYSIS. Chemical analysis by means of absorption or emission of radiation, primarily in the near UV, visible, and infrared portions of the electromagnetic spectrum. It includes such techniques as spectrophotometry, spectrochemical analysis, Raman spectroscopy, colorimetry, and fluorescence measurements. 

In terms of what is measured or observed, there are (1) portions of the electromagnetic spectrum gamma-ray, cosmic ray, x-ray, ultraviolet, infrared, far-infrared, microwave, and radiowave instruments (2) regions pertaining to the energies of particles beta ray (electrons), protons, neutrons, and mass associated instruments and (3) instruments dealing with other spectra such as radioactive decay and Mossbauer effects. 

X-RAY ANALYSIS. X-rays occupy that portion of the electromagnetic spectrum between 0.01 and 100 angstroms (A). Their range of approximate quantum energy is from 2 x 10-6 to 2 x 10 10 erg, or from 106 to 100 eV. Important X-ray analytical methods are based upon (1) fluorescence (2) emission (3) absorption and (4) diffraction. These methods are used qualitatively and quantitatively to determine the element content of complex mixtures and to determine exactly the atomic arrangement and spacings of crystalline materials. See also Ion Microprobc Mass Analyzer. 

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