Which of the following series in H-spectra occurs in IR region

Options

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

Answer

To determine which series in the hydrogen spectrum occurs in the infrared (IR) region, we can follow these steps:

### Step 1: Understand the Regions of the Electromagnetic Spectrum
The electromagnetic spectrum is divided into several regions, including:
- Infrared (IR)
- Visible
- Ultraviolet (UV)

### Step 2: Identify the Series in Hydrogen Spectrum
The hydrogen spectrum consists of several series based on the transitions of electrons between energy levels:
1. **Lyman series**: Transitions to n=1 (UV region)
2. **Balmer series**: Transitions to n=2 (Visible region)
3. **Paschen series**: Transitions to n=3 (IR region)
4. **Bracket series**: Transitions to n=4 (IR region)
5. **Pfund series**: Transitions to n=5 (Far IR region)

### Step 3: Determine Which Series Falls in the IR Region
From the list above, we can see that:
- The **Paschen series** (n=3) and the **Bracket series** (n=4) are the series that occur in the infrared region.

### Conclusion
The series in the hydrogen spectrum that occurs in the infrared region are the **Paschen series** and the **Bracket series**.

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