An electron microscope having a resolving power of less than 50A has been built and used to examine photographic emulsions. When photographic crystals are exposed to an electron beam, silver ions move within the crystals and metallic silver is produced. Also the crystals disintegrate, cracks and holes developing. Pictures have been made showing very small particles of silver formed within silver bromide crystals when they are exposed to an intense light source. Silver reduced from silver bromide by the common chemical developers has been found to have a filamentary structure rather than the “cokelike” form as previously believed. Physical development produces clumps of closely packed silver particles. The smallest photographic crystals (Lippmann crystals), when developed in the common developers, are converted into single threads or ribbons of silver.
© 1941 Optical Society of AmericaFull Article | PDF Article
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