A nucleus is bombarded with a high-speed neutron so that resulting nucleus is a radioactive one. This phenomenon is called

Options

A. Artificial radioactivity
B. Fusion
C. Fission
D. Radioactivity

Answer

To solve the question, we need to understand the process described when a nucleus is bombarded with high-speed neutrons, resulting in a radioactive nucleus. The steps to arrive at the answer are as follows:

### Step-by-Step Solution:

1. **Understanding the Process**: When a high-speed neutron collides with a heavy nucleus, it can cause the nucleus to become unstable. This is because the neutron adds to the total number of nucleons (protons and neutrons) in the nucleus, which can disrupt the balance of forces holding the nucleus together.

**Hint**: Think about what happens when an extra particle is added to a nucleus. Does it make the nucleus more stable or unstable?

2. **Formation of Unstable Nucleus**: The addition of the neutron leads to an intermediate stage where the nucleus is unstable. This unstable nucleus will not remain in this state for long and will seek to reach a more stable configuration.

**Hint**: Consider the concept of stability in nuclear physics. What happens to unstable nuclei?

3. **Decay of Unstable Nucleus**: The unstable nucleus will eventually undergo a decay process, which typically involves splitting into two smaller nuclei (daughter nuclei) along with the release of additional neutrons and a significant amount of energy.

**Hint**: What is the term used when a large nucleus splits into smaller nuclei and releases energy?

4. **Identifying the Phenomenon**: The process described above, where a heavy nucleus splits into smaller nuclei due to the bombardment of neutrons, is known as nuclear fission. This is a well-known phenomenon in nuclear physics and is the principle behind nuclear reactors and atomic bombs.

**Hint**: Recall the definition of nuclear fission. What is the key characteristic of this process?

5. **Conclusion**: Therefore, the phenomenon described in the question is called **nuclear fission**.

### Final Answer:
The phenomenon is called **nuclear fission**.