Text-book of general physics, for the use of colleges and scientific schools (1899)
Hastings, Charles Sheldon · Boston: Ginn & company · leaf 729
s surface in a given time, the intensitywill be 718 SENSATIONS OF COLOR. Similarly, if another sphere be drawn at a distance, d, then,since the amount of energy which passes both surfaces isthe same, the intensity at any point in the second spherewill be E whence(1) I = I I d2 or, in general, the… … Fig. 464. to produce equal illumination upon a screen. In practicethere are a great variety of ways of arranging the apparatus,but as the measurement of intensity neither demands norindeed admits of great precision, a description of two simpleforms will sufficiently illustrate the process. In the…
Physics
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