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 102
rors being reversible a second balancecan be obtained and the mean taken as the result thus eliminatingany error which might arise from dissimilarity in either thesides of the screen or in the mirrors. Referring to the figureboth sides of the screen s s are viewed through the eye-piece oby means of… … Fig. 31.—The Bunsen photometer. The edges of the openings exactly coincide on the two sides ofthe screen. This screen like the Bunsen may be either of thecontrast or disappearance type and, since the edges of the trans-lucent portion are more sharply defined than those of the Bunsen,less difficulty…
Light · Photometry · Electric lighting
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