A lens which is thinner at the middle and thicker at the edges is called a ______ lens.

Options

A. convex
B. concave
C. cylindrical
D. none of these

Answer

To solve the question, "A lens which is thinner at the middle and thicker at the edges is called a ______ lens," we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Types of Lenses**:
- There are two main types of lenses: convex lenses and concave lenses.

2. **Identify the Characteristics of Each Lens**:
- **Convex Lens**: A convex lens is thicker in the middle and thinner at the edges. It converges light rays that are coming parallel to its principal axis.
- **Concave Lens**: A concave lens is thinner in the middle and thicker at the edges. It diverges light rays that are coming parallel to its principal axis.

3. **Analyze the Description Given in the Question**:
- The question describes a lens that is "thinner at the middle and thicker at the edges." This matches the characteristics of a concave lens.

4. **Select the Correct Answer**:
- Based on the analysis, the lens that is thinner at the middle and thicker at the edges is called a **concave lens**.

### Final Answer:
A lens which is thinner at the middle and thicker at the edges is called a **concave lens**.

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