Which lens is thicker in the middle and thinner at its periphery.

Options

A. convex
B. bi-concave
C. concave
D. plano-concave.

Explanation

To solve the question "Which lens is thicker in the middle and thinner at its periphery?", we can follow these steps:

### Step-by-Step Solution:

1. **Understand Lens Types**:
- There are two main types of lenses: convex and concave.
- Convex lenses are thicker in the middle and thinner at the edges, while concave lenses are thinner in the middle and thicker at the edges.

2. **Identify the Characteristics of a Convex Lens**:
- A convex lens is also known as a converging lens.
- It bulges outward, which means it has a greater thickness at the center compared to the edges.

3. **Identify the Characteristics of a Concave Lens**:
- A concave lens is known as a diverging lens.
- It curves inward, making it thinner in the center and thicker at the edges.

4. **Analyze the Options**:
- Given the characteristics, we can analyze the options provided:
- **Option 1: Convex Lens** - Thicker in the middle, thinner at the edges (Correct).
- **Option 2: Concave Lens** - Thinner in the middle, thicker at the edges (Incorrect).
- **Option 3: Biconcave Lens** - Similar to the concave lens, thinner in the middle (Incorrect).

5. **Conclusion**:
- Based on the analysis, the lens that is thicker in the middle and thinner at its periphery is the **Convex Lens**.

### Final Answer:
The lens that is thicker in the middle and thinner at its periphery is the **Convex Lens**.

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