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

Options

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

Answer

### Step-by-Step Solution:

1. **Understanding Silver Halides**:
- Silver halides, such as AgBr, AgCl, and AgI (except AgF), are compounds that are sensitive to light. This means they can undergo a chemical change when exposed to light.

2. **Photosensitivity**:
- The key property that makes silver halides useful in photography is their photosensitivity. When these compounds are exposed to light, they decompose and produce free silver, which appears black. The reaction for AgBr is:
\[ 2 \text{AgBr} \overset{\text{light}}{\rightarrow} 2 \text{Ag} + \text{Br}_2 \]

3. **Formation of Latent Image**:
- In photographic films, a mixture of silver nitrate (AgNO₃) and ammonium bromide (NH₄Br) is used to create an emulsion. When the film is exposed to light, the areas that receive more light will undergo more decomposition, resulting in a latent image.

4. **Development Process**:
- After exposure, the film is treated with a developer solution containing a reducing agent. This reduces the exposed silver halides to metallic silver, making the image visible. The areas that were least exposed remain unchanged.

5. **Fixing the Image**:
- The remaining unexposed silver halides are removed using a hypo solution (fixer), which makes the image permanent.

6. **Conclusion**:
- The primary reason silver halides are used in photography is their photosensitive nature, which allows them to decompose in light and produce a visible image.

### Final Answer:
Silver halides are used in photography because these compounds are photosensitive in nature, allowing them to decompose in light and form free silver, which creates a visible image.

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