Assertion: The surface charge densities of two spherical conductors of different radii are equal. Then the electric field intensities near their surface are also equal.
Reason: Surface charge density is equal to charge per unit area.

Options

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

Answer

To solve the given problem, we need to analyze the assertion and the reason provided, and determine their validity.

### Step-by-Step Solution:

1. **Understanding the Assertion**: The assertion states that if two spherical conductors have equal surface charge densities, then the electric field intensities near their surfaces are also equal.

2. **Surface Charge Density Formula**: The surface charge density (σ) is defined as the charge (Q) per unit area (A). For a sphere, the surface area (A) is given by \( A = 4\pi r^2 \). Thus, the surface charge density can be expressed as:
\[ \sigma = \frac{Q}{4\pi r^2} \]

3. **Electric Field Near the Surface of a Sphere**: The electric field (E) just outside the surface of a charged conductor can be calculated using Gauss's law. The electric field due to a charged sphere is given by:
\[ E = \frac{KQ}{r^2} \]
where K is Coulomb's constant.

4. **Relating Charge to Surface Charge Density**: From the surface charge density formula, we can express the charge (Q) in terms of surface charge density (σ) and radius (r):
\[ Q = \sigma \cdot 4\pi r^2 \]

5. **Calculating Electric Field for Both Spheres**:
- For the first sphere with radius \( r \):
\[ E_1 = \frac{KQ_1}{r^2} = \frac{K(\sigma \cdot 4\pi r^2)}{r^2} = K \cdot 4\pi \sigma \]
- For the second sphere with radius \( R \):
\[ E_2 = \frac{KQ_2}{R^2} = \frac{K(\sigma \cdot 4\pi R^2)}{R^2} = K \cdot 4\pi \sigma \]

6. **Comparing Electric Fields**: Since both expressions for \( E_1 \) and \( E_2 \) simplify to the same value \( K \cdot 4\pi \sigma \), we conclude that:
\[ E_1 = E_2 \]
Therefore, the assertion is correct.

7. **Understanding the Reason**: The reason states that surface charge density is equal to charge per unit area. This is a true statement, but it does not directly explain why the electric fields are equal when the surface charge densities are equal.

8. **Conclusion**: Both the assertion and the reason are correct statements, but the reason does not adequately explain the assertion. Therefore, the final answer is that both the assertion and reason are correct, but the reason is not the correct explanation for the assertion.

### Final Answer:
Both the assertion and reason are correct, but the reason is not the correct explanation for the assertion.