Formation of Latent Imgae Flashcards
This theory describes the process by which invisible changes occur in silver halide crystals upon exposure to light or X-rays, leading to the creation of a latent image that can later be developed into a visible photograph.
THE GURNEY-MOTT THEORY
When a photosensitive material, such as radiographic film, is exposed to light or X-rays, the incident photons interact with silver halide crystals present in the film’s emulsion.
Exposure to Radiation
Each absorbed photon imparts energy to a silver halide crystal, causing the ejection of an electron from a halide ion (e.g., bromide or iodide). This process creates a free electron and leaves behind a positively charged halide ion.
Photon Absorption and Electron Ejection
The free electron migrates through the crystal lattice and becomes trapped at a specific site known as a sensitivity center. This center now carries a negative charge due to the trapped electron.
Electron Trapping at Sensitivity Centers
The negatively charged sensitivity center attracts positively charged silver ions (Ag⁺) from the crystal lattice. When a silver ion reaches the sensitivity center, it gains an electron (is reduced) and becomes a neutral silver atom (Ag⁰).
Attraction of Silver Ions
This process repeats, with multiple silver ions being reduced and accumulating at the sensitivity center, forming a small cluster of metallic silver atoms
Formation of Metallic Silver Clusters
These microscopic clusters of metallic silver constitute the latent image. Although invisible to the naked eye, these clusters represent areas of the film that have been exposed to radiation.
Creation of the Latent Image
During film development, the exposed film is immersed in a developer solution that provides additional electrons to the sensitivity centers.
Development Process
The developer accelerates the reduction of remaining silver ions in the exposed crystals, leading to the growth of metallic silver clusters.
Amplification of Silver Reduction
As these clusters enlarge, they become visible as dark areas on the film, corresponding to the regions that received more exposure. Unexposed areas remain largely unaffected, resulting in the formation of a visible image that accurately represents the varying intensities of the original exposure.
Formation of Visible Image
has been instrumental in advancing the understanding of photographic processes
Gurney-Mott theory
