Optical study for the absorbing crystal

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Purpose: Reconfirmation of the research of Tokugoro Shoda which clarified the fact that two sorts of the elliptically polarized light propagate in a crystal is intended.Specimen: The rock specimen is a hypabyssal rock (Nepheline syenite) from Taquari, Pocos de Caldas, Minas Gerais, Brazil, which is collected at July 26th 1987 in aid of the Science Grant of the Ministry of Education (62041024). It is lent from Geological Museum, Geological Survey of Japan, National Institute of Advanced Industrial Science and Technology. Mineral composition are two sort of amphiboles (Potassic magnesioarfvedsonite and calcic arfvedonite), K-feldspar, Na-feldspar, aegirine, zircon, sphene and pyrite etc. The optical properties of potassic magnesioarfvedsonite is so unique to be elucidated.Construction of an elliptically polarizing microscope: The main body of the newly constructed microscope is the system polarizing microscope BX-P made by OLYMPUS OPTICAL CO., LTD. A mercury lamp (SHL-100UVQ-2, produced … More by Harison Toshiba Lighting Corp. is used as a light source. A narrow band path filter CJ43177 supplied by Edmund Industrial Optics is inserted in the optical path to select a monochromatic light of the 546nm wave length. Two rotatable quarter wave plates are set; the lower one is between the polarizer and the stage and upper one is between the stage and the analyzer. The direction of the lower quarter wave plate is measured from the direction that the vibrating direction of the faster wave in the plate coincide to the direction of the polarizer.Construction of analytical system: A Logitec middle tower personal computer LPC-PTIGBS with the software of Image-Pro Plus by Media Cybernetics is introduced to analyze the image of a CCD camera (SONY CCD-IRIS DXC-108).Observation: One of amphibole crystals shows incomplete extinction under the conventional polarizing microscope. On the case that the lower quarter wave plate is rotated 13 degrees to the anti-clock direction from the zero point and the upper quarter wave plate is hold to the appropriate direction corresponding to the lower, the complete extinction is observed. This means that the elliptically polarized light of the ellipticity of 0.23 can propagate in this crystal.Result: This observation guarantees the validity of the theory proposed by T. Shoda. Less