Under what conditions of electronic transition will the emitted light be monochromatic ?

Explanation

To determine the conditions under which emitted light will be monochromatic during electronic transitions, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding Electronic Transitions**:
- Electrons in an atom can occupy different energy levels. When an electron transitions from a higher energy level (E2) to a lower energy level (E1), it emits energy in the form of light.

2. **Energy of Emitted Light**:
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