Abstract
Both magnesium carbonate and magnesium oxide are used in laboratories as reflectors of visible radiation and a knowledge of their spectral characteristics is desirable. The method here used to measure coefficients of reflection depends on the variation of brightness within a spherical integrator when a section of the surface is removed or added. The photometry was done with a Macbeth instrument and interference filters were used to get six zones in the spectrum. The centroids were computed for low levels of luminosity. By taking photometric readings with three part-spheres of different degrees of completeness, the coefficients can be computed for three different combinations, and comparison of results indicates the consistency of results. The average coefficient of magnesium carbonate was found to be about 0.983, while that of the oxide was about 0.991, and both have a slight selectivity in favor of the red end of the spectrum.
© 1948 Optical Society of America
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