Assertion: No net charge can exist in the region where electric field is uniform.
Reason: For any type of Gaussian surface selected within the region of a uniform electric field, the angle between electric field intensity and area normal is `90^@` everywhere. Hence, electric flux linked with the selected Gaussian surface is equal to zero. If the net electric flux is zero for some Gaussian surface then according to Gauss's law the net charge enclosed within the surface must be zero.

Options

A. If both assertion and reason are correct and reason is a correct explanation of the assertion .
B. If both assertion and reason are correct but reason is not the correct explanation of assertion
C. If assertion is correct but reason is incorrect
D. If assertion is incorrect but reason is correct.

Answer

To solve the given question, we need to analyze both the assertion and the reason provided.

### Step-by-Step Solution:

1. **Understanding the Assertion**:
The assertion states that "No net charge can exist in the region where the electric field is uniform." A uniform electric field means that the electric field has the same magnitude and direction at every point in that region.

2. **Applying Gauss's Law**:
According to Gauss's Law, the electric flux (Φ) through a closed surface is proportional to the charge (Q) enclosed within that surface:
\[ \Phi = \frac{Q_{\text{in}}}{\epsilon_0} \]
where \( \epsilon_0 \) is the permittivity of free space.

3. **Electric Flux in a Uniform Electric Field**:
If we consider a Gaussian surface in a uniform electric field, the electric field lines will enter and exit the surface. For a closed surface in a uniform electric field, the amount of electric field lines entering the surface will equal the amount exiting, leading to a net electric flux of zero:
\[ \Phi_{\text{net}} = \Phi_{\text{in}} - \Phi_{\text{out}} = 0 \]

4. **Conclusion from Gauss's Law**:
Since the net electric flux is zero, according to Gauss's Law, the net charge enclosed within the Gaussian surface must also be zero:
\[ Q_{\text{in}} = 0 \]
This supports the assertion that no net charge can exist in a region with a uniform electric field.

5. **Understanding the Reason**:
The reason states that "For any type of Gaussian surface selected within the region of a uniform electric field, the angle between electric field intensity and area normal is 90 degrees everywhere." This is incorrect because, while the electric field may be uniform, it does not necessarily mean that the angle between the electric field and the area vector (normal) of the surface is always 90 degrees. For example, in the case of a cylindrical surface aligned with the electric field, the lateral surface has an angle of 0 degrees with the electric field.

6. **Final Evaluation**:
The assertion is correct, but the reason is incorrect. Therefore, the correct answer is:
- Assertion is true, Reason is false.

### Final Answer:
The assertion is correct, but the reason is incorrect. Thus, the answer is C.