Assertion: In both radio actiivity and photoelectric effect electrons may be ejected.
Reason: In photoelectric effect and radio activity emission occurs only of unstable elements.

Options

A. 1. If both assertion and reason are true and reason is the correct explanation of assertion.
B. 2. If both assertion and reson are true but reason is not the correct explanation of assertion.
C. 3. if assertion is true but reason is false.
D. 4. If both assertion and reason are false.

Answer

To solve the question, we need to analyze both the assertion and the reason provided.

### Step-by-Step Solution:

1. **Understanding the Assertion**:
- The assertion states that in both radioactivity and the photoelectric effect, electrons may be ejected.
- In the photoelectric effect, when light (photons) strikes a metal surface, it can provide enough energy to eject electrons from that surface. This phenomenon is well-established in physics.

2. **Understanding the Reason**:
- The reason provided states that the photoelectric effect and radioactive emission occur only in unstable elements.
- The photoelectric effect does not require the material to be unstable; it can occur in stable metals as well. Therefore, this part of the reason is incorrect.

3. **Evaluating the Assertion and Reason Together**:
- Since the assertion is true (electrons can be ejected in both phenomena) and the reason is false (the photoelectric effect does not require unstable elements), we conclude that the assertion is true, but the reason is false.

4. **Final Conclusion**:
- Based on the analysis, the correct answer is that the assertion is true, but the reason is false.

### Answer:
- The answer is **C**: Assertion is true, but Reason is false.