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2006
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December
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In the Laboratory
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Refractive Index Determination of Transparent Polymers: Experimental Setup for Multi-Wavelength Determination and Calculation at Specific Frequencies Using Group Contribution Theory
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Jay Dlutowski, Andres M. Cardenas-Valencia, David Fries, and Larry Langebrake
Center for Ocean Technology, Marine Science College, University of South Florida, St. Petersburg, FL 33626
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December 2006
Vol. 83 No. 12
p. 1867
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| Abstract |
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A simple and relatively inexpensive experimental lab that clearly shows the dependence of light reflection on the angle of incidence for transparent polymers is described. Light transmission measurements are used to quantify the reflection magnitude and can in turn be used for determining the real term of the refractive index, n, of the material. A tungsten-filament lamp and a fiber-optic spectrophotometer are used for the experiments, which demonstrate the dependence of n on wavelength. Two polymeric materials are used: PMMA plates and in-house prepared PDMS slides from a commercial resin. Additionally, the simplicity of functional chemical group contribution theory, as material property predictor based on the material's chemical structure, is exemplified by calculating the refractive index of PMMA using molar refractivities. Molar refractivites from three approaches, Lorentz and Lorenz, Gladstone and Dale, and Vogel, are used to calculate the refractive index. Close agreement between the experimentally obtained and calculated values are observed (at a wavelength of 589 nm).The described laboratory also contains the pertinent modeling for relating the observed transmitted light signals with index of refraction, providing the opportunity to design other pedagogical assignments that tie first-principles modeling with experimentation.
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| Supplement |
Instructions for the students and notes for the instructor are available.
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| More Information |
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Citation |
Dlutowski, Jay; Cardenas-Valencia, Andres M.; Fries, David; Langebrake, Larry. J. Chem. Educ. 2006 83 1867.
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Keywords |
Analytical Chemistry; Hands-On Learning / Manipulatives; Laboratory Instruction; Physical Properties; Polymer Chemistry; Polymerization; Second-Year Undergraduate; Upper-Division Undergraduate; UV-Vis Spectroscopy
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History |
Created:
Last Updated: |
10/30/2006
11/7/2006
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 Caution! | | Experiments, laboratory exercises, lecture demonstrations, and other descriptions of the use of chemicals, apparatus, instruments, computers, and computer interfaces are presented in the Journal of Chemical Education as illustrative of new or improved ideas or concepts in chemistry instruction and are directed at qualified teachers. Although every effort is made to assure and encourage safe practices and safe use of chemicals, the Journal of Chemical Education cannot assume responsibility for uses made of its published materials. Many chemicals are hazardous. Precautions for the safe use of hazardous chemicals and directions for their proper disposal are described in the Material Safety Data Sheets and on the labels. We strongly urge all those planning to use materials from our pages to make choices and to develop procedures for laboratory and classroom safety in accordance with local needs and situations. |
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2006
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1867
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