Infrared radiation, ranges

The first requirement is a source of infrared radiation that emits all frequencies of the spectral range being studied. This polychromatic beam is analyzed by a monochromator, formerly a system of prisms, today diffraction gratings. The movement of the monochromator causes the spectrum from the source to scan across an exit slit onto the detector. This kind of spectrometer in which the range of wavelengths is swept as a function of time and monochromator movement is called the dispersive type. 

Long-wave radiation (infrared radiation) is in the range of 0.8-100 i.m, short-wave radiation (visible as light) is in the range 0.4-0.8 [Lin, and solar radiation is in the range 0.3-3.0 juim. 

The main sources of infrared radiation used in spectrophotometers are (1) a nichrome wire wound on a ceramic support, (2) the Nernst glower, which is a filament containing zirconium, thorium and cerium oxides held together by a binder, (3) the Globar, a bonded silicon carbide rod. These are heated electrically to temperatures within the range 1200- 2000 °C when they will glow and produce the infrared radiation approximating to that of a black body. 

C07-0056. Refer to Figure 7 4 to answer the following questions (a) What is the wavelength range for infrared radiation (b) What color is light whose wavelength is 4.85 X 10 m (c) hi what... 

Optical principles are based on the fact that technical gases have distinct absorption spectra in different wavelength ranges of electromagnetic radiation. The widespread infrared spectral photometries uses the fact, that certain gases absorb infrared radiation in a characteristic manner. 02 and N2 are IR-inactive and therefore other compounds in air or flue gas can be easily detected. This technique has a very high selectivity for single compounds and shows only a few cross-sensitivities. 

The wavelength range of infrared radiation lies between 700 nm and 1 X 106nm (1 mm) but because of the large numerical values involved in quot-... 

Black body radiators are used as sources of infrared radiation in the range 2-15 yum, e.g. the Nemst glower, which consists of a hollow rod made of the fused oxides of zirconium, yttrium and thorium. For use it is preheated and, when a voltage is applied, it emits intense continuous infrared radiation with very little visible radiation. 

Detection of the middle and far range of infrared radiation requires thermal detectors, the simplest of which is a thermocouple, in which the change in temperature at one junction of the thermocouple results in a small voltage being produced. Although simple in design, thermocouples lack sensitivity. Bolometers are more sensitive and are based on the fact that as the temperature of a conductor... 

The optical features of a center depend on the type of dopant, as well as on the lattice in which it is incorporated. For instance, Cr + ions in AI2O3 crystals (the ruby laser) lead to sharp emission lines at 694.3 nm and 692.8 nm. However, the incorporation of the same ions into BeAl204 (the alexandrite laser) produces a broad emission band centered around 700 nm, which is used to generate tunable laser radiation in a broad red-infrared spectral range. 

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