Which of the following statement (s) is`//`are correct (may have more than one option correct):

Options

A. the rest mass of a stable nucleus is less than sum of the rest masses of its separated nucleons.
B. the rest mass of a stable nucleus is greater than the sum of the rest masses of its separated nucleons.
C. in nuclear fission energy is released by fusing two nuclei of medium mass ( approximately 100 amu).
D. in nuclear fission energy is released by fragmentation of a very heavy nucleus.

Answer

To solve the question regarding which statements about nuclear physics are correct, we will analyze each option provided in the video transcript step by step.

### Step 1: Analyze the First Statement
**Statement 1:** The rest mass of a stable nucleus is less than the sum of the rest mass of its separated nucleons.

**Explanation:** This statement is correct. In nuclear physics, this phenomenon is known as mass defect. When nucleons (protons and neutrons) come together to form a nucleus, some mass is converted into binding energy (as per Einstein's equation E=mc²). Therefore, the rest mass of the nucleus is indeed less than the sum of the rest masses of the individual nucleons.

### Step 2: Analyze the Second Statement
**Statement 2:** Energy is released by fusing two nuclei of medium mass.

**Explanation:** This statement is also correct. In nuclear fusion, when two light nuclei combine to form a heavier nucleus, energy is released. However, the statement is somewhat misleading as it implies that medium mass nuclei are involved. Fusion typically occurs with light nuclei (like hydrogen isotopes) rather than medium mass nuclei.

### Step 3: Analyze the Third Statement
**Statement 3:** Energy is released by the fragmentation of very low nuclei.

**Explanation:** This statement is incorrect. The fragmentation of very low mass nuclei typically refers to processes such as fission, where a heavy nucleus splits into smaller nuclei. Energy is released in fission, but not from the fragmentation of very low mass nuclei.

### Step 4: Analyze the Fourth Statement
**Statement 4:** Heavy nuclei are unstable and undergo radioactive decay.

**Explanation:** This statement is generally correct. Heavy nuclei tend to be unstable and often undergo radioactive decay to reach a more stable configuration. This is a well-known principle in nuclear physics.

### Conclusion
Based on the analysis:
- **Correct Statements:** 1, 2, and 4
- **Incorrect Statement:** 3

### Final Answer
The correct statements are 1, 2, and 4.

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