Assertion : A convex lens made of material of refractive index 1.2 behaves as diverging lens when kept in water of refractive index `4//3`.
Reason : A convex lens made of material of refractive index 1.2 behaves as converging lens when placed in air.

Options

A. If both assertion and reason are correct and rason 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 assertion-reason question, we need to analyze both statements and determine their validity.

### Step 1: Analyze the Assertion
The assertion states that "A convex lens made of material of refractive index 1.2 behaves as a diverging lens when kept in water of refractive index 4/3 (or 1.33)."

1. **Understanding Refractive Indices**:
- The refractive index of the lens (n_lens) = 1.2
- The refractive index of water (n_water) = 1.33

2. **Comparison**:
- Since n_lens (1.2) < n_water (1.33), the lens will behave differently in water compared to air.

3. **Behavior of the Lens**:
- A convex lens typically converges light when placed in a medium with a lower refractive index than itself (like air).
- However, when placed in a medium with a higher refractive index (like water in this case), the lens behaves as a diverging lens.

### Conclusion for Assertion:
The assertion is **true**.

### Step 2: Analyze the Reason
The reason states that "A convex lens made of material of refractive index 1.2 behaves as a converging lens when placed in air."

1. **Understanding Refractive Indices in Air**:
- The refractive index of air (n_air) is approximately 1.

2. **Comparison**:
- Since n_lens (1.2) > n_air (1), the lens will behave as a converging lens in air.

3. **Behavior of the Lens**:
- A convex lens converges light when placed in a medium with a lower refractive index than itself (like air).

### Conclusion for Reason:
The reason is **true**.

### Step 3: Determine the Relationship
Now, we need to check if the reason correctly explains the assertion.

- The assertion is about the behavior of the lens in water, while the reason discusses its behavior in air.
- Although both statements are true, the reason does not explain why the lens behaves as a diverging lens in water.

### Final Conclusion:
Both the assertion and reason are correct, but the reason does not provide a correct explanation for the assertion. Therefore, the answer is:

**Option 2**: Both assertion and reason are correct, but the reason is not the correct explanation of the assertion.

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