Assertion : When two soap bubbles having different radii are kept in contact , the common surface at their interface will bulge into a large bubble .
Reason : Pressure inside the smaller bubble is larger .

Options

A. Assertion is True , Reason is True , Reason is a correct explanation for Assertion
B. Assertion is true , Reason is true , Reason is not a correct explanation for Assertion
C. Assertion is True , Reason is False
D. Assertion is false , Reason is true.

Answer

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

### Step-by-Step Solution:

1. **Understanding the Assertion**:
- The assertion states that when two soap bubbles of different radii are in contact, the common surface will bulge into a larger bubble.
- Let's denote the radius of the smaller bubble as \( R_1 \) and the radius of the larger bubble as \( R_2 \) (where \( R_2 > R_1 \)).

2. **Understanding the Reason**:
- The reason given is that the pressure inside the smaller bubble is larger than that inside the larger bubble.
- According to the formula for excess pressure in a soap bubble, the excess pressure \( P \) is given by:
\[ P = \frac{4T}{R} \]
where \( T \) is the surface tension and \( R \) is the radius of the bubble.

3. **Comparing Pressures**:
- For the smaller bubble (radius \( R_1 \)):
\[ P_1 = \frac{4T}{R_1} \]
- For the larger bubble (radius \( R_2 \)):
\[ P_2 = \frac{4T}{R_2} \]
- Since \( R_1 < R_2 \), it follows that \( P_1 > P_2 \). This means the pressure inside the smaller bubble is indeed larger than that inside the larger bubble.

4. **Effect of Pressure Difference**:
- The difference in pressure between the two bubbles will cause the interface between them to bulge towards the larger bubble. The higher pressure in the smaller bubble pushes against the lower pressure in the larger bubble, resulting in the bulging of the interface.

5. **Conclusion**:
- Since both the assertion and the reason are true, and the reason correctly explains the assertion, we conclude that the assertion is true and the reason is also true, with the reason being a correct explanation of the assertion.

### Final Answer:
- **Assertion**: True
- **Reason**: True
- **Explanation**: The pressure inside the smaller bubble is larger, causing the interface to bulge into the larger bubble.