The emission spectrum of an atomic gas in a magnetic field differs from that of the gas in the absence of a magnetic field. Which of the following is true of the phenomenon?
A. It is called the Stern-Gerlach effect
B. It is called the Stark effect
C. It is due primarily to the nuclear magnetic moment of the atoms
D. The number of emission lines observed for the gas in a magnetic field is always twice the number observed in the absence of a magnetic field.
E. The number of emission lines observed for the gas in a magnetic field is either greater than or equal to the number observed in the absence of a magnetic field
(GR8677 #82)
Solution:
Zeeman Effect: the splitting of a spectral line into several components in the presence of a static magnetic field.→ A and B are FALSE.
In most atoms, there exist several electron configurations with the same energy (degeneracy), so that transitions between these configurations and another correspond to a single spectral line.
The presence of a magnetic field breaks this degeneracy, since the magnetic field interacts differently with electrons with different quantum numbers, slightly modifying their energies. → C is FALSE.
The result is that, where there were several configurations with the same energy, they now have different energies, giving rise to several very close spectral lines.
image: physics.cornell.edu (click image to enlarge)
→ E is TRUE as opposed to D
Answer: E
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