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. The exposed part of the film or plate after developing contains

Options

A. Silver metal
B. Silver oxide
C. Silver bromide
D. Silver nitrate

Answer

To solve the question regarding the composition of the exposed part of the photographic film or plate after developing, we can follow these steps:

### Step 1: Understanding the Composition of Photographic Film
Photographic films are made by adding a 20% aqueous solution of silver nitrate (AgNO₃) to ammonium bromide (NH₄Br) in the presence of gelatin. This mixture leads to the formation of silver bromide (AgBr), which is the key photosensitive component.

**Hint:** Recall that silver halides, especially AgBr, are crucial in photography due to their photosensitivity.

### Step 2: Photosensitivity of Silver Halides
Silver bromide (AgBr) is photosensitive, meaning it undergoes a chemical change when exposed to light. When exposed to light, AgBr decomposes into free silver (Ag) and bromine (Br₂).

**Hint:** Remember that the decomposition reaction is essential for understanding how images are formed in photography.

### Step 3: The Decomposition Reaction
The decomposition reaction of silver bromide can be represented as follows:
\[ 2 \text{AgBr} \xrightarrow{\text{light}} 2 \text{Ag} + \text{Br}_2 \]
This reaction indicates that when AgBr is exposed to light, it produces free silver (Ag), which is responsible for the darkening of the film.

**Hint:** Focus on the products of the decomposition reaction to identify what is present in the exposed areas.

### Step 4: Development of the Film
After exposure, the film is treated with a developer that contains a reducing agent. This process enhances the visibility of the image by reducing the silver ions that have been formed in the exposed areas to metallic silver.

**Hint:** The developer plays a critical role in making the latent image visible by further reducing the silver ions.

### Step 5: Final Composition of the Exposed Film
After developing, the exposed parts of the film contain metallic silver (Ag) due to the reduction of the silver ions formed during the exposure to light. This metallic silver appears black on the film, creating the visible image.

**Hint:** The key takeaway is that the visible image on the developed film is primarily due to the presence of metallic silver.

### Conclusion
Thus, the exposed part of the film or plate after developing contains **silver metal (Ag)**.

**Final Answer:** The exposed part of the film or plate after developing contains silver metal.