Question

Name the chemical used in black and white photography.

Answer 1

Hint: To answer this question, you should recall that traditional black and white photography utilized a chemical process that has been observed since ancient times – that of the photo-sensitivity of silver compounds. The reaction involves a halogen and a rare metal.

Complete step by step answer:
- As evidenced by the colour schemes produced by particular types of film or by trends in digital processing, colour can sometimes suggest a specific era. A lack of colour in a photograph often accentuates the light and shadows. Backlit subjects and dramatic shadows are brought to the audience’s attention quickly in black and white images. Many fine art photographers prefer black and white images for their tendency to distance the subject matter from reality.
- Silver bromide is water-insoluble salt known for its unusual sensitivity to light and this property has allowed silver halides to become the basis of modern photographic materials. In the presence of light decomposition of silver bromide gives silver, which turns grey on exposure to light. That is the reason it is always kept in the dark bottles.
- The reaction of silver chloride with sunlight is also called a photolytic decomposition reaction in which the decomposition reaction is carried out by sunlight.
This reaction can be represented by the reaction:
\[2AgBr \to {\text{ }}2Ag{\text{ }} + {\text{ }}B{r_2}\]

Note:
This ability was harnessed by the19th century photography pioneers by coating silver halides i.e. molecules of \[Ag\] and halide gases in an emulsion of gelatin onto a glass or plastic backer. The process of making the traditional film has not changed much from the basic chemical reactions. Initially, elemental silver is reacted with nitric acid to form silver nitrate.