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 132
iffusibility so that itsillumination varies according to the cosine law and be so locatedthat neither the instrument nor the operator will interceptany light which would otherwise fall upon it. With dueregard to these features the photometer was constructed asshown in Fig. 54. For a sensitive… … Fig. 54.—Side elevation of Sharp-Millar photometer. The photometrical balance may be obtained by varying thedistance between the comparison lamp and the screen. Anelectric lamp was chosen for the comparison source as wouldnaturally be expected and either a low voltage lamp of thebattery type or one…
Light · Photometry · Electric lighting
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