Name the spectral series of hydrogen atom, which be in infrared region.

Options

A. Lyman
B. Balmer
C. Brackett, Paschen and Pfund
D. All of these

Answer

To answer the question regarding the spectral series of the hydrogen atom that lies in the infrared region, we can follow these steps:

### Step-by-Step Solution:

1. **Understanding Spectral Series**:
The hydrogen atom emits light at specific wavelengths when electrons transition between energy levels. These transitions result in spectral series.

2. **Identifying the Series**:
There are five main spectral series for the hydrogen atom:
- Lyman series
- Balmer series
- Paschen series
- Brackett series
- Pfund series

3. **Determining the Regions**:
Each of these series corresponds to different regions of the electromagnetic spectrum:
- The **Lyman series** corresponds to ultraviolet light.
- The **Balmer series** corresponds to visible light.
- The **Paschen series**, **Brackett series**, and **Pfund series** correspond to infrared light.

4. **Focusing on the Infrared Region**:
The question specifically asks for the series that falls within the infrared region. From our identification:
- The **Paschen series** (n=3 to n=2 transitions)
- The **Brackett series** (n=4 to n=2 transitions)
- The **Pfund series** (n=5 to n=2 transitions)

5. **Conclusion**:
The spectral series of the hydrogen atom that lie in the infrared region are:
- **Paschen series**
- **Brackett series**
- **Pfund series**

### Final Answer:
The spectral series of the hydrogen atom that lie in the infrared region are the **Paschen series, Brackett series, and Pfund series**.

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