The magnetic susptibility of an ideal diamagnetic substance is

Options

A. `-1`
B. 0
C. `+1`
D. `oo`

Explanation

To solve the question regarding the magnetic susceptibility of an ideal diamagnetic substance, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding Magnetic Susceptibility**:
- Magnetic susceptibility (χ) is a dimensionless quantity that indicates how much a material will become magnetized in an applied magnetic field. It is defined as the ratio of the magnetization (M) of the material to the applied magnetic field strength (H).

2. **Characteristics of Diamagnetic Substances**:
- Diamagnetic substances are materials that create an opposing magnetic field when exposed to an external magnetic field. This results in a very weak repulsion from the magnetic field.

3. **Magnetic Susceptibility of Diamagnetic Materials**:
- For diamagnetic materials, the magnetic susceptibility is always negative. This is because they oppose the applied magnetic field. The susceptibility for ideal diamagnetic substances is typically in the range of -1 < χ < 0.

4. **Ideal Diamagnetic Substance**:
- An ideal diamagnetic substance would have a magnetic susceptibility of χ = -1. This means that it perfectly opposes the magnetic field without any residual magnetization.

5. **Conclusion**:
- Therefore, the magnetic susceptibility of an ideal diamagnetic substance is χ = -1.

### Final Answer:
The magnetic susceptibility of an ideal diamagnetic substance is **-1**.

---