A : Lenses of large aperture suffer from spherical aberration.
R : The curvature of the lens at central and peripheral regions is different.

Options

A. If both Assertion & Reason are true and the reason is the correct explanation of the assertion, then mark (1).
B. If both Assertion & Reason are true but the reason is not the correct explanation of the assertion, then mark (2).
C. If Assertion is true statement but Reason is false, then mark (3).
D. If both Assertion and Reason are false statements, then mark (4).

Answer

To analyze the given assertion and reason, we can break down the problem step by step.

### Step 1: Understand the Assertion
The assertion states that "lenses of large aperture suffer from spherical aberration."

- **Explanation**: A lens with a large aperture allows more light to enter, but it also means that light rays coming from different parts of the lens (especially the edges) will converge at different points. This leads to a blurred or vague image, which is known as spherical aberration.

### Step 2: Understand the Reason
The reason states that "the curvature of the lens at central and peripheral regions is different."

- **Explanation**: The curvature of a lens affects how light rays are refracted. In a perfect lens, the curvature should be uniform to ensure that all rays converge at the same focal point. However, in a lens with a large aperture, the rays that pass through the central part (paraxial rays) and the rays that pass through the edges (marginal rays) do not converge at the same point due to the difference in curvature. This is a contributing factor to spherical aberration.

### Step 3: Analyze the Relationship Between Assertion and Reason
Now, we need to determine if the reason correctly explains the assertion.

- The assertion is true because lenses of large aperture do indeed suffer from spherical aberration.
- The reason is also true in that the curvature difference contributes to this aberration. However, the statement that "the curvature of the lens at central and peripheral regions is different" may not be entirely accurate in the context of spherical aberration, as it implies a fundamental design flaw rather than a consequence of the large aperture.

### Conclusion
Both the assertion and the reason are true, but the reason does not fully explain the assertion. Therefore, the correct answer is that the assertion is true, but the reason is not a valid explanation for the assertion.

### Final Answer
Assertion (A) is true, and Reason (R) is true, but R is not the correct explanation for A.

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