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 assertion-reason question regarding beta decay, we will analyze both the assertion and the reason step by step.

### Step 1: Understand the Assertion
The assertion states: "In beta decay, an electron is emitted by the nucleus."

**Explanation**:
- Beta decay is a type of radioactive decay where a neutron in the nucleus is transformed into a proton, and in this process, an electron (beta particle) is emitted.
- Specifically, in beta minus decay, a neutron (which has no charge) is converted into a proton (which has a positive charge) and an electron (which has a negative charge) is emitted along with an antineutrino.

### Step 2: Understand the Reason
The reason states: "Electrons are not present inside the nucleus."

**Explanation**:
- In atomic structure, the nucleus contains protons and neutrons. Electrons are found outside the nucleus, orbiting around it in various energy levels or shells.
- Therefore, the statement that electrons are not present inside the nucleus is correct.

### Step 3: Analyze the Relationship
Now, we need to determine if the reason provided correctly explains the assertion.

- The assertion is true because beta decay involves the emission of an electron from the nucleus.
- The reason is also true as electrons are indeed not found inside the nucleus.

However, the reason does not explain why the assertion is true. The emission of an electron during beta decay is due to the transformation of a neutron into a proton, not simply because electrons are absent from the nucleus.

### Conclusion
- Both the assertion and reason are true, but the reason does not provide a correct explanation for the assertion. Therefore, the correct answer is that the assertion is true, the reason is true, but the reason is not a correct explanation of the assertion.

### Final Answer
The correct option is: Assertion and reason are true, but reason is not a correct explanation of the assertion.

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