Light, photometry and illumination : a thoroughly rev. ed. of ''Electrical illuminating engineering'' (1912)
Barrows, William Edward, 1878-1960 · New York ; London : McGraw-Hill Book Co. · leaf 106
RY 91 plaster-of-Paris G which receives the light from the two sourcesand which is viewed through the telescopic combination asshown. Two biprisms located at Z^ and Z^ at right angles toeach other present the illuminated fields in the shape of fourquadrants, alternate ones of which are illuminated…
Light · Photometry · Electric lighting
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