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 determine which series of the hydrogen spectrum lies completely in the ultraviolet region, we need to analyze the different series of spectral lines produced by hydrogen transitions.

### Step-by-Step Solution:

1. **Understand the Series of Hydrogen Spectrum**:
- The hydrogen spectrum consists of several series based on the electron transitions between energy levels. The main series are:
- Lyman series
- Balmer series
- Paschen series
- Brackett series

2. **Identify the Regions of Each Series**:
- **Lyman Series**: This series corresponds to transitions where electrons fall to the first energy level (n=1). All the lines in this series are in the ultraviolet region.
- **Balmer Series**: This series corresponds to transitions where electrons fall to the second energy level (n=2). The lines in this series are in the visible region.
- **Paschen Series**: This series corresponds to transitions where electrons fall to the third energy level (n=3). The lines in this series are in the near-infrared region.
- **Brackett Series**: This series corresponds to transitions where electrons fall to the fourth energy level (n=4). The lines in this series are in the far-infrared region.

3. **Conclusion**:
- From the analysis above, it is clear that the only series that lies completely in the ultraviolet region is the **Lyman series**.

Thus, the answer to the question is **Lyman series**.