A: In `beta`-decay an electron is emitted by the nucleus
R: Electrons are not present inside the nucleus.

Options

A. if both assertion & reason are true and the reason is correct explanation of the assertion then mark (1)
B. if both assertion & reason are true and the reason is not correct explanation of the assertion then mark (2)
C. if assertion is true statement but reason is false then mark (3)
D. if both assertion & reason are false then mark (4)

Answer

To solve the question, we need to analyze the assertion (A) and the reason (R) provided:

**Assertion (A):** In beta decay, an electron is emitted by the nucleus.
**Reason (R):** Electrons are not present inside the nucleus.

### Step-by-Step Solution:

1. **Understanding Beta Decay:**
- Beta decay is a type of radioactive decay where a nucleus emits a beta particle. This beta particle can be an electron (β-) or a positron (β+).
- In β- decay, a neutron in the nucleus is transformed into a proton, and an electron (beta particle) is emitted. This process increases the atomic number by 1.

2. **Analyzing the Assertion (A):**
- The assertion states that in beta decay, an electron is emitted by the nucleus. This is true, as during β- decay, an electron is indeed emitted as a result of the transformation of a neutron into a proton.

3. **Analyzing the Reason (R):**
- The reason states that electrons are not present inside the nucleus. This is also true. The nucleus is made up of protons and neutrons (collectively called nucleons), while electrons exist in the electron cloud surrounding the nucleus.

4. **Evaluating the Relationship Between A and R:**
- While both the assertion and the reason are true, the reason does not provide a correct explanation for the assertion. The emission of an electron during beta decay is a nuclear process, and the fact that electrons are not present in the nucleus does not explain why an electron is emitted.

5. **Conclusion:**
- Both the assertion (A) and the reason (R) are true, but the reason is not the correct explanation for the assertion. Therefore, the correct answer is that both A and R are true, but R is not the correct explanation of A.

### Final Answer:
Both Assertion (A) and Reason (R) are true, but R is not the correct explanation of A.

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