X.—The Law of Blackening of the Photographic Plate at Low Densities. (Third Paper.)

Abstract

SummaryOf a number of absorbing and emitting systems subjected to radiation, the proportions which suffer given sequences of absorptions and emissions are examined. The simple results which follow when the proportions so affected are small are applied to the photographic action on the assumption that in exposure the grain acts as a single system. They indicate that the grain requires two absorptions in succession to render it susceptible to “full” development, and three absorptions with one intermediate “emission” to render it susceptible to “partial” development, the terms “full” and “partial” being defined. These results are found to apply over the whole range of wave-length tested, from 4800 Å. to below 2000 Å.