Sodium thiosulphate is used in photography

Options

A. To convert metallic silver into silver salt
B. AgBr grain is reduced to non-metallic silver
C. To remove reduced silver
D. To remove undercomposed AgBr in the form of `Na_(3)[Ag[S_(2)O_(3))_(2)]` (a complex salt)

Explanation

### Step-by-Step Solution:

1. **Understanding Sodium Thiosulfate**: Sodium thiosulfate is a chemical compound with the formula Na2S2O3. It is commonly used in various applications, including photography.

**Hint**: Remember the chemical formula and its components.

2. **Role in Photography**: In photography, sodium thiosulfate acts as a fixing agent. Its primary role is to remove unreacted silver halides from the photographic film after exposure.

**Hint**: Think about the process of developing photographs and the need to remove excess materials.

3. **Chemical Reaction**: When exposed to light, silver bromide (AgBr) in the photographic emulsion is reduced to metallic silver (Ag). Sodium thiosulfate then reacts with the remaining silver halides, converting them into soluble silver thiosulfate complexes.

**Hint**: Consider the transformation of silver halides during the photographic process.

4. **Final Reaction**: The overall reaction can be simplified as follows:
- Sodium thiosulfate reacts with silver bromide (AgBr) to form soluble complexes, which can then be washed away, leaving behind only the developed image.

**Hint**: Focus on the importance of removing unreacted materials to preserve the image.

5. **Conclusion**: Thus, sodium thiosulfate is crucial in photography as it ensures that only the desired image remains on the film by eliminating unwanted silver halides.

**Hint**: Summarize the importance of sodium thiosulfate in the photographic process.