In the figure of previous problem, `D` and `E` respectively represent

Options

A. Absorption line of Balmer series and the ionisation potential of hydrogen
B. Absorption line of Balmer series and the wavelength lesser than lowest of the Lyman series
C. Spectral line of Balmer series and the maximum wavelegth of Lyman series
D. Spectral line of Lyman series and the absorption to greater wavelength of limiting value of Paschen series

Answer

To solve the problem regarding what `D` and `E` represent in the context of the hydrogen spectrum, we can follow these steps:

### Step-by-Step Solution:

1. **Identify the Context**:
- The question refers to a previous problem that dealt with the spectral lines of hydrogen, specifically the transitions between energy levels.

2. **Analyze Transition D**:
- Transition `D` corresponds to an electron moving from a higher energy level (n=4) to a lower energy level (n=2).
- This transition falls within the Balmer series, which involves transitions to n=2 from higher levels (n=3, n=4, etc.).
- Therefore, we can conclude that `D` represents an **absorption line corresponding to the Balmer series**.

3. **Analyze Transition E**:
- Transition `E` corresponds to an electron moving from an infinite energy level (n=∞) to the ground state (n=1).
- This transition is significant because it represents the ionization potential of hydrogen, as it indicates the energy required to remove an electron from the atom completely.
- Additionally, this transition corresponds to the Lyman series, which involves transitions to n=1 from higher levels (n=2, n=3, etc.).
- Thus, `E` represents the **ionization potential of hydrogen**.

4. **Summarize Findings**:
- Based on the analysis, we can summarize:
- `D` represents an **absorption line of the Balmer series**.
- `E` represents the **ionization potential of hydrogen**.

### Final Answer:
- `D` corresponds to an absorption line of the Balmer series.
- `E` corresponds to the ionization potential of hydrogen.