Question

Which of the following salts are used in photography?
1. AgCl
2. AgBr
3. AgI
4. All of the above

Answer 1

Correct Answer - Option 4 : All of the above

Concept:

• AgCl, AgBr, AgF and AgI are known as Silver Halides.
• A silver halide is one of the chemical compounds that can form between the element silver and one of the halogens.
• Silver halides are light-sensitive chemicals.

Explanation:

• Silver halides are used in black and white photography.
• A photographic film is coated with silver halide. When light falls on the surface, the exposed part of the film is darkened from which photograph is developed. That’s why it is used in photography.
• The salts are reduced to the metal form when light falls on them.

AgCl + hν → Ag⁺ + Cl + 1 electron

Ag+ + 1 e^- → Ag

• When silver metal is formed, it forms a dark image on the film.
• When we take a picture, the camera lens projects a small but accurate image on the surface of this light-sensitive layer, and the silver bromide is decomposed more or less, depending on the intensity of the light received in various points of the image.
• Hence, silver halides for its unusual sensitivity to light are used in photography.