Of the various series of the hydrogen spectrum, the one which lies completely in the ultraviolet region is

Options

A. Lyman series
B. Balmer series
C. Paschen series
D. Brackett series

Answer

To solve the question regarding which series of the hydrogen spectrum lies completely in the ultraviolet region, we can follow these steps:

### Step-by-Step Solution:

1. **Understand the Hydrogen Spectrum**: The hydrogen spectrum consists of various series resulting from electronic transitions between energy levels in a hydrogen atom. Each series corresponds to transitions from a higher energy level (n) to a lower energy level (n).

2. **Identify the Series**: The major series of the hydrogen spectrum include:
- Lyman Series (n=1)
- Balmer Series (n=2)
- Paschen Series (n=3)
- Brackett Series (n=4)
- Pfund Series (n=5)

3. **Determine the Wavelength Ranges**:
- **Lyman Series**: Transitions to n=1 (ultraviolet region)
- **Balmer Series**: Transitions to n=2 (visible region)
- **Paschen Series**: Transitions to n=3 (infrared region)
- **Brackett Series**: Transitions to n=4 (infrared region)
- **Pfund Series**: Transitions to n=5 (infrared region)

4. **Identify the Ultraviolet Series**: The Lyman series is the only series that involves transitions to the n=1 energy level, and all its wavelengths fall within the ultraviolet region. The wavelengths for the Lyman series are approximately less than 4000 angstroms.

5. **Conclusion**: Since the Lyman series is the only series that lies completely in the ultraviolet region, the answer to the question is the Lyman series.

### Final Answer:
The series of the hydrogen spectrum that lies completely in the ultraviolet region is the **Lyman Series**.

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