An implies that a perfect diamagnet is a supercondutor. This implies that when a super conductor is put in a magnetic field of intensity B, the magnetic field `B_(s)` inside the superconductor will be such that :

Options

A. `B_(s)= -B`
B. `B_(s)=0`
C. `B_(s)=B`
D. `B_(s) lt B` but Bs `ne0`

Explanation

To solve the question regarding the magnetic field inside a superconductor when placed in an external magnetic field, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding Superconductors**:
- A superconductor is a material that can conduct electricity without resistance below a certain critical temperature. This means that its resistivity becomes zero.

2. **Properties of Perfect Diamagnetism**:
- A perfect diamagnet is a material that completely expels magnetic fields from its interior when placed in an external magnetic field. This phenomenon is known as the Meissner effect.

3. **Application of the Meissner Effect**:
- When a superconductor is placed in an external magnetic field, it will exhibit perfect diamagnetism. This means that the magnetic field inside the superconductor will be expelled.

4. **Conclusion on Magnetic Field Inside the Superconductor**:
- Since the superconductor expels the magnetic field due to its perfect diamagnetic properties, the magnetic field intensity \( B_s \) inside the superconductor will be zero.

5. **Final Answer**:
- Therefore, we conclude that \( B_s = 0 \).