Zeeman effect refers to the

Options

A. splitting of the spectral lines in a magnetic field
B. Splitting up of the spectral lines in an electrostatic field
C. Emission of electrons from metals when light falls on it
D. Random scattering of `alpha` - particles by gold foil

Answer

**Step-by-step Solution:**

1. **Understanding the Question**: The question asks about the Zeeman effect and provides four options. We need to identify which option correctly describes the Zeeman effect.

2. **Defining the Zeeman Effect**: The Zeeman effect refers to the phenomenon where spectral lines of atoms are split into multiple components when the atoms are placed in a strong magnetic field. This splitting occurs due to the interaction between the magnetic field and the magnetic moments associated with the angular momentum of the electrons.

3. **Analyzing the Options**:
- **Option A**: "Splitting of the spectral lines in a magnetic field" – This is a correct definition of the Zeeman effect.
- **Option B**: "Splitting of the spectral lines in an electrostatic field" – This describes the Stark effect, not the Zeeman effect.
- **Option C**: "Emission of electrons from metals when light falls on it" – This refers to the photoelectric effect, which is unrelated to the Zeeman effect.
- **Option D**: "Random scattering of alpha particles by gold foil" – This describes Rutherford scattering, which is also unrelated to the Zeeman effect.

4. **Conclusion**: Based on the definitions and analysis of the options, the correct answer is **Option A**: "Splitting of the spectral lines in a magnetic field."

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