Assertion:- Paraxial rays are always parallel to the principal axis.
Reason:- A parallel beam parallel to principal axis converges at the focal point.

Options

A. If both Assertion `&` Reason are True `&` the Reason is a correct explanation of the Assertion.
B. If both Assertion `&` Reason are True but Reason is not a correct explanation of the Assertion.
C. If Assertion is True but the Reason is False.
D. If both Assertion `&` Reason are False.

Answer

To analyze the given assertion and reason, we will break down the statements and evaluate their validity step by step.

### Step 1: Understanding the Assertion
**Assertion:** Paraxial rays are always parallel to the principal axis.

- **Definition of Paraxial Rays:** Paraxial rays are those rays that are very close to the principal axis of a lens or mirror. They are not necessarily parallel to the principal axis but are close enough that they can be approximated as such for the purpose of ray optics.
- **Conclusion for Assertion:** The assertion is **false** because paraxial rays are not always parallel to the principal axis; they are simply close to it.

### Step 2: Understanding the Reason
**Reason:** A parallel beam parallel to the principal axis converges at the focal point.

- **Behavior of Parallel Rays:** When a parallel beam of light (which is indeed parallel to the principal axis) strikes a converging lens or a concave mirror, it converges at the focal point. This is a fundamental property of lenses and mirrors.
- **Conclusion for Reason:** The reason is **true** because it accurately describes the behavior of parallel rays with respect to converging optics.

### Step 3: Evaluating the Relationship Between Assertion and Reason
- The assertion is false, while the reason is true. Therefore, the overall statement that "the assertion is true and the reason is true" is incorrect.

### Final Conclusion
- The assertion is false, and the reason is true. Hence, the answer is that the assertion is false, and the reason is true.

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