Laurence, Lionel · London, School of Optics · leaf 35
which is placed a rod. The standard isplaced (preferably at one foot) in front of the screen and the rod casts ashadow. The luminant (Fig. 18) to be measured is placed so far away that SHADOWS AND PHOTOMETRY 23 the shadow cast by the rod from its light is of equal intensity to that ofthe other. The… … Fia. 18. of illuminations that are actually compared, although apparently it is theshadows themselves. Tbe lights should be placed so that the two shadowslie near to each other without overlapping. The Iuminant measured is of somany candle-power according to the distance at which the shadow…
Optics
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