The splitting of spectral lines in an external magnetic field is known as the

Options

A. Zeeman effect
B. Stark effect
C. photoelectric effect
D. None of these

Answer

**Step-by-Step Solution:**

1. **Understanding the Question**: The question asks about the phenomenon where spectral lines split when an external magnetic field is applied.

2. **Identifying the Effect**: The phenomenon of spectral line splitting in the presence of an external magnetic field is known as the **Zeeman Effect**.

3. **Explanation of the Zeeman Effect**: The Zeeman Effect occurs because the energy levels of electrons in an atom are affected by the external magnetic field. This causes the orbitals of the electrons to split into multiple sub-levels.

4. **Role of Quantum Numbers**: The degree of splitting depends on the orbital quantum number (denoted as L) of the electrons. Each orbital can have different magnetic quantum numbers (denoted as mL), which correspond to the different orientations of the orbitals in the magnetic field.

5. **Conclusion**: Therefore, the splitting of spectral lines in an external magnetic field is specifically referred to as the **Zeeman Effect**.

**Final Answer**: The splitting of spectral lines in an external magnetic field is known as the **Zeeman Effect**.

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