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conantee
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« on: January 07, 2010, 09:43:01 PM »

82. 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 absenced 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.
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« Reply #1 on: October 15, 2010, 11:12:33 AM »

This question might be difficult for people who never encountered atomic/nuclear physics. There are unfamiliar technical terms and experiment names. However, you can see that the last choice sounds most general but true. In presence of magnetic field, the number of energy levels might increase due to Hamiltonian perturbation. The number of energy levels might be the same too due to insensitivity of atoms (magnetic moment is zero).

The correct answer is (E). 39 of 100 people got the correct one.

Note: Stern-Gerlach effect is the test for spin of particles done by particles beam, not gas. Stark effect is perturbation by E-field. Both of them are not quite related to this question. 
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