Direct Measurement of Standard Reflectances with the Microphotometer

A. F. Hallimond

Summary: A visual microphotometer depending on three polarizing screens is used to provide the primary scale for measuring the ratio of intensity between the incident and reflected beams for a prepared standard surface, which is intended for subsequent use in the ordinary procedure with the ore-microscope. A reversing mirror on the microscope stage gives reflection at quasi-normal incidence. Direct measurements on a surface of diamond confirm the validity of the Fresnel formula for a polished surface of this substance, and there is general agreement for a series of transparent bodies ranging up to 17 % reflectance. The standard is a glass-covered metallic surface with a reflectance near 50 %. For pyrite RD = 54·5 %.

Mineralogical Magazine; June 1957 v. 31; no. 237; p. 487-494; DOI: 10.1180/minmag.1957.031.237.07
© 1957, The Mineralogical Society
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