spect - A Double Beam Spectrometer A QuickTime movie and a...

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A Double Beam Spectrometer A QuickTime movie and a (soundless) GIF animation are both available that illustrate the workings of a double beam spectrophotometer. Introduction The following is a brief description of a double beam spectrophotometer. The purpose of this instrument is to determine the amount of light of a specific wavelength absorbed by an analyte in a sample. Although samples can be gases or liquids, an analyte dissolved in a solvent is discussed here. [In the infrared, solid pellets using an IR. transparent matrix (like a high purity salt such as Kr) can be used for solid analytes. Thin disks are made using a pellet press and the disk suspended in the sample cell through which the sample beam passes.] The starting point in our movie is the light s o u r c e . Depending on the wavelength of interest, this can be an electrically powered ultraviolet, visible, or infrared lamp. Not shown in the animations that accompany this page is the spectrophotometer's monochromator which selects the analytical wavelength from the source lamp's broad spectrum containing many wavelengths of light. The analytical wavelength is chosen based on the absorbance characteristics of the analyte. Monochromators are instruments whose sole purpose is to allow polychromatic (that is many wavelength containing) light into the entrance slit of the monochromator and only allow a single (or at least very few) wavelength (monochromatic light) out via the exit slit . This exiting, well-shaped, narrowly-defined beam now contains a small region of the electromagnetic spectrum. The spread, or band-pass, of the wavelengths depends
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This note was uploaded on 03/03/2012 for the course CHEM 100 taught by Professor Chasteen during the Fall '06 term at Sam Houston State University.

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spect - A Double Beam Spectrometer A QuickTime movie and a...

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