Assertion In water, value of magnetic field decreases.
Reason: Water is a diamagnetic substance. When diamagnetic material is placed in

Options

A. If both assertion and reason are true and reason is the correct explanation of assertion.
B. If both assertion and reason are true and reason is not the correct explanation of assertion.
C. If assertion is ture but reason is false.
D. If both assertion and reason are false.

Explanation

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

### Step-by-Step Solution:

1. **Understanding the Assertion**:
- The assertion states that "In water, the value of the magnetic field decreases."
- This means that when we place a magnetic field in water, its strength is less than that in a vacuum or air.

2. **Understanding the Reason**:
- The reason states that "Water is a diamagnetic substance."
- Diamagnetic substances are materials that have a relative permeability less than 1. This means they are weakly repelled by magnetic fields.

3. **Connecting Assertion and Reason**:
- Since water is a diamagnetic substance, it will exhibit a decrease in the magnetic field strength when exposed to an external magnetic field. This is due to the fact that diamagnetic materials create an opposing magnetic field when placed in an external magnetic field, leading to a net decrease in the magnetic field strength.

4. **Conclusion**:
- Both the assertion and the reason are true. The reason provided accurately explains why the assertion is correct. Therefore, the correct option is that both the assertion and the reason are true, and the reason is the correct explanation of the assertion.

### Final Answer:
Both the assertion and reason are true, and the reason is the correct explanation of the assertion.

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