The variation of magnetic susceptibility `(chi)` with temperature for a diamagnetic substance is best represented by

Options

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Explanation

To solve the question regarding the variation of magnetic susceptibility (χ) with temperature for a diamagnetic substance, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding Magnetic Susceptibility (χ)**:
- Magnetic susceptibility (χ) is a measure of how much a material will become magnetized in an applied magnetic field. It indicates the degree of magnetization of a material in response to an external magnetic field.

2. **Characteristics of Diamagnetic Substances**:
- Diamagnetic materials have a negative susceptibility (χ < 0). This means they are weakly repelled by a magnetic field.
- The susceptibility of diamagnetic materials is generally very small and negative.

3. **Temperature Dependence**:
- For diamagnetic substances, the magnetic susceptibility is independent of temperature. This means that regardless of the temperature changes, the value of χ remains constant.

4. **Graphical Representation**:
- Since χ is negative and constant with respect to temperature, the graph representing this relationship would be a horizontal line below the temperature axis (indicating negative values) that does not change as temperature varies.

5. **Conclusion**:
- The variation of magnetic susceptibility (χ) with temperature for a diamagnetic substance is best represented by a horizontal line that remains constant (negative) across different temperatures.

### Final Answer:
The variation of magnetic susceptibility (χ) with temperature for a diamagnetic substance is best represented by a horizontal line below the temperature axis, indicating that it is negative and independent of temperature.