Refractive Index Determination of Transparent Polymers: Experimental Setup for Multi-Wavelength Determination and Calculation at Specific Frequencies Using Group Contribution Theory

• Jay Dlutowski ^[1] ; Andres M. Cardenas-Valencia ^[1] ; David Fries ^[1] ; Larry Langebrake ^[1]
  1. [1] University of South Florida

     University of South Florida

     Estados Unidos

     
• Localización: Journal of chemical education, ISSN 0021-9584, Vol. 83, Nº 12, 2006, pág. 1867
• Idioma: inglés
• Texto completo no disponible (Saber más ...)
• Resumen

  • 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.