Mechanism of Formation
The action of the light with the silver halide grains within the emulsion forms sites of metallic silver on the grains. The basic mechanism by which this happens was first proposed by R W Gurney and N F Mott in 1938. The incoming photon liberates an electron from a silver halide molecule, called photoelectron. Photoelectrons migrate to a shallow electron trap site (a sensitivity site), where the electrons reduce silver ions to form a metallic silver speck. A positive hole must also be generated but it is largely ignored. Subsequent work has slightly modified this picture, so that 'hole' trapping is also called into question (Mitchell, 1957). Since then, the mechanism of sensitivity and latent image formation has been greatly improved.
Read more about this topic: Latent Image
Famous quotes containing the words mechanism of, mechanism and/or formation:
“A mechanism of some kind stands between us and almost every act of our lives.”
—Sarah Patton Boyle, U.S. civil rights activist and author. The Desegregated Heart, part 3, ch. 2 (1962)
“When one of us dies of cancer, loses her mind, or commits suicide, we must not blame her for her inability to survive an ongoing political mechanism bent on the destruction of that human being. Sanity remains defined simply by the ability to cope with insane conditions.”
—Ana Castillo (b. 1953)
“The formation of an oppositional world view is necessary for feminist struggle. This means that the world we have most intimately known, the world in which we feel “safe” ... must be radically changed. Perhaps it is the knowledge that everyone must change, not just those we label enemies or oppressors, that has so far served to check our revolutionary impulses.”
—Bell (c. 1955)