The chemical used as a fixer/developer in photography is
Sodium sulphate
Sodium sulphide
Sodium thiosulphate
Sodium sulphite
Answer is Right!
Answer is Wrong!
This question was previously asked in
UPSC NDA-1 – 2015
In photography, after development (where exposed silver halide is converted to metallic silver), the fixer bath is used to remove the *unexposed* silver halide crystals from the film or paper. Sodium thiosulphate dissolves these unexposed crystals, making the image permanent and no longer sensitive to light. While Sodium sulphite can be a component of developer solutions (as a preservative), Sodium thiosulphate is the primary chemical used as a *fixer*. Given the “fixer/developer” phrasing and the options, sodium thiosulphate is the most definitive answer for a chemical used in one of these key steps, specifically fixing.