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 question, we need to analyze the assertion and reason provided:

**Assertion (A):** A photon cannot transfer all of its energy to an isolated electron.
**Reason (R):** When the energy of a photon is more than 1.02 MeV, it can materialize into two particles called electron and positron.

### Step-by-Step Solution:

1. **Understanding Photon Energy:**
- The energy of a photon is given by the equation \( E = h \nu \), where \( h \) is Planck's constant and \( \nu \) is the frequency of the photon.
- In the context of this problem, we need to consider the interaction between a photon and an isolated electron.

2. **Energy Transfer to an Isolated Electron:**
- When a photon interacts with an isolated electron, it can transfer energy to the electron. However, due to the principles of conservation of momentum and energy, a single photon cannot completely transfer all of its energy to an isolated electron.
- If a photon were to transfer all its energy to an electron, it would violate the conservation laws because the electron would need to gain a corresponding momentum, which is not possible in an isolated system.

3. **Photon Energy Greater than 1.02 MeV:**
- The reason states that when the energy of a photon exceeds 1.02 MeV, it can materialize into an electron and a positron.
- This is based on the principle of pair production, which occurs when a photon has enough energy (greater than 1.02 MeV, which is the combined rest mass energy of an electron and a positron) to create a particle-antiparticle pair.

4. **Conclusion on Assertion and Reason:**
- Both the assertion (A) and the reason (R) are true statements.
- However, the reason (R) does not correctly explain the assertion (A). The assertion is about the inability of a photon to transfer all its energy to an isolated electron, while the reason discusses the conditions for pair production, which is a different phenomenon.

5. **Final Answer:**
- Therefore, the correct conclusion is that both the assertion and reason are true, but the reason is not the correct explanation of the assertion. Hence, the option that states this is correct.