A course of experiments in physical measurement (1897)
Whiting, Harold, d. 1895 · Boston, D.C. Heath and Co. · leaf 258
s by a set ofcovers (6, c, and d~). Alldirect light is thus ex-cluded from the photome-ter. A cloth cover, a, may-be thrown over the headwhen it is desired to com-pare very feeble illumina-tions. Box photometers mayalso be constructed onBunsens or on Rumfordsprinciple. They have theadvantage of a… … Fig. 99. See 228 RADIATION. [Ext-. 40. ^ 115. Errors in Photometry due to Color Blind-ness. — Light is essentially a physiological as distin-guished from a physical quantity. There is nostandard by which we may prove that one kind oflight is more brilliant than another. A person who is color-blind…
Physics
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