A photographic film was exposed to a measured quantity of monochromatic light-energy at 2536A, and the resulting number of silver bromide grains rendered developable by the exposure was determined by a direct microscopic count. It was thus possible to calculate the energy required to render developable a single grain of silver bromide. A mercury arc and an ultra-violet monochromator provided the monochromatic light-energy. Quantitative measurements of light-energy were made with a linear thermopile in combination with a Thomson galvanometer of figure of merit 4 X 10-10 amp/mm. One candle-meter on the thermopile gave a galvanometer deflection of 1500 mm. Preliminary results at this wave-length show that about 800 quanta are required to render a grain developable. Exposures made at other regions in the ultra-violet will be reported upon at a later date.
Proceedings of the Iowa Academy of Science
©1923 Iowa Academy of Science, Inc.
Helmick, P. S.
"The Light-Energy of 2536A Required to Render Developable a Grain of Silver Bromide,"
Proceedings of the Iowa Academy of Science, 30(1), 75-75.
Available at: https://scholarworks.uni.edu/pias/vol30/iss1/15