Photography is based on the nature of silver halides. Except AgF, the silver halides are photosensitive. These undergo decomposition in light and turn black due to formation of free silver.
`2AgBroverset(light)to2Ag+Br_2`
The photography films are prepared by adding `20%` aqueous solution of `AgNO_3` to `NH_4Br` solution containing gelatic. When such a film is exposed, emulsion gets affected and a latent image is formed on the film.
When this exposed film or plate is dipped ina developer which contains a reducing agent, the part affected most during exposure are reduced to the maximum. The image becomes visible. It is called a negative. The remaining sensitive emulsion on the negative is removed by dissolving it in hypo solution (fixer). Fihnally, a positive of the nagative already prepared is made on silver bromide paper.
Q. Silver halides are used in photographgy because these compounds
A. are insoluble in water
B. are affected by light
C. are soluble in ammonia solution
D. easily stick on the surface of photographic plate or film
