Why is `AgBr` used in photography ?

Answer

To answer the question "Why is AgBr used in photography?", we can break down the explanation into several key points:

### Step-by-Step Solution:

1. **Understanding Silver Halides**:
- Traditional film photography relies on the light sensitivity of silver halide crystals, which include compounds like silver bromide (AgBr). These crystals are essential components in photographic films.

2. **Light Sensitivity**:
- When the film is exposed to light, the silver halide crystals undergo a chemical change. This exposure is crucial as it initiates the process of capturing an image.

3. **Formation of Latent Image**:
- Upon exposure to light, the silver bromide crystals change to record a latent image. This latent image is not immediately visible but can be developed into a photograph later.

4. **Reduction to Metallic Silver**:
- AgBr is particularly light sensitive among the silver halides. When exposed to light, it undergoes a reduction reaction, converting to metallic silver. This metallic silver forms the visible part of the photograph.

5. **Development Process**:
- After exposure, the film is developed. During this process, unexposed AgBr can be removed. This is typically done by treating the film with a solution of sodium thiosulfate (Na2S2O3), which dissolves the unexposed AgBr.

6. **Final Outcome**:
- The result of this process is a developed photograph where the areas that were exposed to light appear dark due to the presence of metallic silver, while the unexposed areas are cleared of AgBr.

### Summary:
AgBr is used in photography because it is highly light sensitive. Upon exposure to light, it forms a latent image by reducing to metallic silver, which can then be developed into a visible photograph. Unexposed AgBr is removed during the development process using sodium thiosulfate.