A : A photon cannot transfer all of its energy to an isolated electron .
R : When energy of a photon is more then 1.02 MeV , It can materialize into two particles called electron and positron .

Options

A. If both Assertion & Reason are ture and the reason is the correct explanation of the assertion , then mark (1) .
B. If both Assertion & Reason are true but the reason is not the 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 and Reason are false statements , then mark (4) .

Answer

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

### Step 1: Analyze the Assertion
The assertion states that "A photon cannot transfer all of its energy to an isolated electron."

- **Explanation**: When a photon collides with an electron, it can transfer energy to the electron, but due to the conservation of momentum, it cannot transfer all of its energy if the electron is isolated and at rest. If the photon were to transfer all its energy, the electron would have to gain infinite momentum, which is not possible. Thus, the assertion is correct.

### Step 2: Analyze the Reason
The reason states that "When energy of a photon is more than 1.02 MeV, it can materialize into two particles called electron and positron."

- **Explanation**: This statement is also correct. According to the principles of quantum mechanics and particle physics, a photon can indeed materialize into an electron-positron pair if its energy exceeds 1.02 MeV (the combined rest mass energy of an electron and a positron). This process is known as pair production. However, this does not directly explain why a photon cannot transfer all its energy to an isolated electron, as pair production involves a different mechanism and conditions.

### Step 3: Conclusion
- The assertion is true, and the reason is also true, but the reason does not provide a valid explanation for the assertion. Therefore, we conclude that the assertion is correct, and the reason is correct but not the correct explanation.

### Final Answer
- Assertion (A) is true.
- Reason (R) is true, but it does not explain (A).

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