For refractive index measurements of solid thin films when film absorption is negligible, the Brewster angle method described by Abeles [ Compt. rend. 228, 553 ( 1949)] is extremely convenient. An apparatus is described which facilitates routine index measurements using this method. A corner mirror system elimates the need for manually tracking the reflected beam as the angle of incidence is varied. Settings are reproducible to within about 0.1% of the index value under optimun conditions, the results agreeing with those of other observers.
A method is described whereby the apparatus may be used for the routine measurement of the indexes of nonabsorbing liquid films.
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