In a photon-particle collision (sauch as photon-electron collision), which of the following may not be conserved ?

Options

A. Total energy
B. Number of photons
C. Total momentum
D. both (a) and (b)

Explanation

To solve the question regarding conservation laws in a photon-particle collision, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Collision**: In a photon-particle collision, we typically consider interactions such as photon-electron collisions. Here, a photon interacts with an electron, which can lead to various outcomes, including absorption or scattering.

2. **Identify Conservation Laws**: In physics, particularly in collisions, we have certain conservation laws that apply:
- **Conservation of Energy**: The total energy before the collision must equal the total energy after the collision.
- **Conservation of Momentum**: The total momentum before the collision must equal the total momentum after the collision.
- **Conservation of Charge**: The total electric charge is conserved in these interactions.

3. **Examine the Options**: The question asks which quantity may not be conserved in a photon-particle collision. The options typically include:
- Total energy
- Total momentum
- Number of photons
- Electric charge

4. **Analyze Each Option**:
- **Total Energy**: This is conserved in all interactions, including photon-particle collisions.
- **Total Momentum**: This is also conserved in these types of collisions.
- **Number of Photons**: This is the key point. In a photon-particle collision, photons can be absorbed by particles (e.g., an electron absorbing a photon), which means the number of photons can change. Additionally, new photons can be emitted as a result of the collision.
- **Electric Charge**: This is conserved in photon-electron interactions as well.

5. **Conclusion**: The quantity that may not be conserved in a photon-particle collision is the **number of photons**. This is because photons can be absorbed or new photons can be created during the interaction.

### Final Answer:
The quantity that may not be conserved in a photon-particle collision is the **number of photons**.

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