Zeeman Effect & Stark Effect
Fine Structure of Spectra | Structure of Atom Class 11
1. Limitation of Bohr's Model
Niels Bohr's model successfully explained the Hydrogen spectrum but failed to explain the fine splitting of spectral lines when the atom is placed in an external field. This splitting indicated that energy shells contain sub-shells.
2. The Zeeman Effect
The splitting of spectral lines into multiple components when the source of light (atom) is placed in a strong Magnetic Field ($B$).
Why does it happen?
Electrons revolving in orbits behave like tiny magnets (creating a magnetic moment). In an external magnetic field, these orbits can orient themselves in specific directions (quantized orientations), leading to slightly different energy levels and thus splitting the spectral lines.
Significance: It introduced the Magnetic Quantum Number ($m_l$).
3. The Stark Effect
The splitting of spectral lines into multiple components when the source of light (atom) is placed in a strong Electric Field ($E$).
Mechanism
The external electric field polarizes the atom, shifting the centers of positive and negative charges. This perturbation alters the energy levels of the orbitals, causing the single spectral line to split into several fine lines.
4. Comparison Table
| Feature | Zeeman Effect | Stark Effect |
|---|---|---|
| External Field | Magnetic Field ($B$) | Electric Field ($E$) |
| Discovered By | Pieter Zeeman (1896) | Johannes Stark (1913) |
| Concept | Interaction of magnetic moment with field | Interaction of electric dipole with field |
| Quantum Number | Relates to Magnetic Quantum No. ($m_l$) | Relates to orbital polarization |
Practice Quiz
Test your knowledge on Spectral Splitting.
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