Assertion: Rayleigh scattering can be considered as elastic collisions of photons with massive particles.
Reason: In Rayleigh scattering. The energy of incident and scattered is same.

Options

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

Explanation

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

### Step 1: Understand the Assertion
The assertion states that "Rayleigh scattering can be considered as elastic collisions of photons with massive particles."

- **Explanation**: In Rayleigh scattering, a photon interacts with a particle (like an atom or a molecule) without any change in the energy of the photon. This means that the photon is scattered elastically, which is a key characteristic of elastic collisions.

### Step 2: Understand the Reason
The reason states that "In Rayleigh scattering, the energy of incident and scattered is the same."

- **Explanation**: This is true because during Rayleigh scattering, the energy of the incoming photon is equal to the energy of the scattered photon. There is no loss of energy in the process, which is a defining feature of elastic scattering.

### Step 3: Conclusion
Both the assertion and the reason are correct. The assertion correctly describes Rayleigh scattering as an elastic collision, and the reason accurately states that the energy of the incident and scattered photons remains the same.

### Final Answer
Since both the assertion and reason are correct, the correct option is **A**.

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