SAT Subject Physics Practice Question 204: Answer and Explanation

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Question: 204

50.

The diagram (not drawn to scale) gives the first few electron energy levels within a single-electron atom. Which of the following gives the energy of a photon that could NOT be emitted by this atom during an electron transition?

A. 17 eV
B. 42 eV
C. 64 eV
D. 255 eV
E. 302 eV

Correct Answer: B

Explanation:

The energies emitted during electron transitions are equal to the differences between the allowed energy levels. A, 17 eV, is equal to the energy emitted by the photon when an electron drops from the –21 eV level to the –38 eV level. C, 64 eV, is equal to the energy emitted by the photon when an electron drops from the –21 eV level to the –85 eV level. D, 255 eV, is equal to the energy emitted by the photon when an electron drops from the –85 eV level to the –340 eV level. And E, 302 eV, is equal to the energy emitted by the photon when an electron drops from the –38 eV level to the –340 eV level. However, no electron transition in this atom could give rise to a 42 eV photon.

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