Assertion: Gauss's theroem can be applied only for a closed surface.
Reason: Electric flux can be obtained passing from an open surface also.

Options

A. If both Assertion and Reason are true but Reason is the correct explanation of Assertion.
B. If both Assertion and Reason are true but Reason is not the correct explanation of Assertion.
C. If Assertion is true, but the Reason is false.
D. If Assertion is false but the Reason is true.

Explanation

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

### Step 1: Understanding Gauss's Theorem
Gauss's theorem states that the electric flux through a closed surface is proportional to the charge enclosed within that surface. Mathematically, it can be expressed as:

\[ \Phi_E = \oint \mathbf{E} \cdot d\mathbf{A} = \frac{Q_{\text{enc}}}{\epsilon_0} \]

where:
- \(\Phi_E\) is the electric flux,
- \(\mathbf{E}\) is the electric field,
- \(d\mathbf{A}\) is the differential area vector on the closed surface,
- \(Q_{\text{enc}}\) is the total charge enclosed,
- \(\epsilon_0\) is the permittivity of free space.

### Step 2: Evaluating the Assertion
The assertion states: "Gauss's theorem can be applied only for a closed surface."

This statement is **true**. Gauss's theorem specifically applies to closed surfaces because it relates the total electric flux through the surface to the charge enclosed within that surface. Open surfaces do not enclose any volume and therefore cannot be used to apply Gauss's theorem.

### Step 3: Evaluating the Reason
The reason states: "Electric flux can be obtained passing from an open surface also."

This statement is also **true**. Electric flux can indeed be calculated through an open surface using the formula:

\[ \Phi_E = \int \mathbf{E} \cdot d\mathbf{A} \]

However, this does not serve as a valid explanation for why Gauss's theorem is limited to closed surfaces. The reason does not directly relate to the assertion about the applicability of Gauss's theorem.

### Step 4: Conclusion
- The assertion is true: Gauss's theorem applies only to closed surfaces.
- The reason is true but does not explain the assertion correctly.

Thus, the final conclusion is that the assertion is true, while the reason is true but not a correct explanation for the assertion.

### Final Answer
- Assertion: True
- Reason: True, but not a correct explanation for the assertion.

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