Assertion (A), Between any two given energy levels, the number of absorption transition is always less than number of emission transition.
Reason (R ): Absorption transitiion start from the lowest energy lovely only and may end at any higher energy level. but emission transition may start from any higher energy level and end at any energy level below it.

Options

A. Statement-1 is True, Statement-2 is True, Statement-2 is a correct explanation for Statement-1
B. Statement-1 is True, Statement-2 is True, Statement-2 is NOT a correct explanation for Statement-1
C. Statement-1 is True, Statement-2 is False.
D. Statement-1 is False, Statement-2 is True.

Answer

To analyze the assertion and reason provided in the question, we can break down the concepts of absorption and emission transitions in quantum mechanics, particularly in the context of energy levels of electrons in an atom.

### Step-by-Step Solution:

1. **Understanding Absorption and Emission Transitions**:
- **Absorption Transition**: This occurs when an electron in an atom absorbs a photon and moves from a lower energy level to a higher energy level. The energy of the photon must match the energy difference between the two levels.
- **Emission Transition**: This occurs when an electron in an atom drops from a higher energy level to a lower energy level, emitting a photon in the process. The emitted photon carries away the energy difference between the two levels.

2. **Energy Levels**:
- Consider two energy levels, say \( E_1 \) (lower) and \( E_2 \) (higher). The electron can absorb energy to jump from \( E_1 \) to \( E_2 \) (absorption).
- For emission, the electron can start from \( E_2 \) and drop to \( E_1 \), or it can drop to any other lower energy level \( E_3 \), \( E_4 \), etc.

3. **Counting Transitions**:
- In the case of absorption, if an electron is in the ground state (lowest energy level), it can only absorb energy to move to a higher level. Therefore, the number of possible absorption transitions is limited to the number of higher energy levels available.
- In contrast, for emission, an electron can start from any higher energy level and can transition to any lower energy level. This means there are more possible paths for emission transitions.

4. **Conclusion on Assertion**:
- Since the number of absorption transitions is limited (it can only go to higher levels from the lowest level), while emission transitions can occur from any higher level to any lower level, it follows that the number of absorption transitions is always less than the number of emission transitions.

5. **Evaluating the Reason**:
- The reason states that absorption transitions start from the lowest energy level and may end at any higher energy level, while emission transitions can start from any higher energy level and end at any lower energy level. This is a correct explanation of the behavior of absorption and emission transitions.

### Final Answer:
- The assertion (A) is true, and the reason (R) is also true and provides a correct explanation for the assertion.