Value of Impact parameter will be zero, when scattering angle is

Options

A. `pi //2`
B. `pi`
C. `2pi/3`
D. `3pi//2`

Explanation

To determine the scattering angle when the impact parameter is zero, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding Impact Parameter**:
- The impact parameter (b) is defined as the perpendicular distance from the center of the nucleus (or scattering center) to the straight-line path of the incoming particle (in this case, an alpha particle).

2. **Condition for Zero Impact Parameter**:
- When the impact parameter is zero, it means that the incoming particle is aimed directly at the center of the nucleus. Thus, the particle will not deviate from its path until it interacts with the nucleus.

3. **Analyzing the Scattering Process**:
- If the alpha particle approaches the nucleus directly (with zero impact parameter), it will interact with the nucleus and will be repelled back along the same line of approach.

4. **Determining the Scattering Angle**:
- The scattering angle is defined as the angle between the direction of the incoming particle and the direction of the outgoing particle after scattering.
- Since the alpha particle is repelled directly back along its original path, the angle it turns is 180 degrees.

5. **Conclusion**:
- Therefore, when the impact parameter is zero, the scattering angle is 180 degrees (or π radians).

### Final Answer:
The value of the impact parameter will be zero when the scattering angle is π (180 degrees).

---