In which transition, one quantum of energy is emitted -

Options

A. `n=4 rarr n=2`
B. `n=3 rarr n=1`
C. `n=4 rarr n=1`
D. `n=2 rarr n=1`

Answer

To solve the question regarding which transition emits one quantum of energy, we need to understand the concept of electron transitions in atomic structure.

### Step-by-Step Solution:

1. **Understanding Quantum Energy Emission**:
- When an electron transitions between energy levels in an atom, it either absorbs or emits energy. The energy emitted corresponds to the difference in energy between the two levels.

2. **Identifying the Energy Levels**:
- In a hydrogen atom (or similar atoms), energy levels are denoted by principal quantum numbers (n). For example, n=1 is the ground state, n=2 is the first excited state, and so on.

3. **Higher to Lower Energy Transition**:
- When an electron moves from a higher energy level (n2) to a lower energy level (n1), it emits energy in the form of a photon. This is the process of energy emission.

4. **Example Transitions**:
- For instance, if an electron transitions from n=4 to n=2, it emits energy. Similarly, transitions from n=3 to n=1, or n=5 to n=3, also involve energy emission.

5. **Conclusion**:
- Therefore, any transition from a higher energy level to a lower energy level will result in the emission of one quantum of energy (one photon).

### Final Answer:
All transitions from a higher energy level to a lower energy level (like n=4 to n=2) will emit one quantum of energy.

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