A Situation Known as "Population Inversion" Is Needed for Lasing

question 12

Multiple Choice

A situation known as "population inversion" is needed for lasing action. What does "population inversion" mean?

• A) Electrons in the ms = 1/2 state switch to −1/2 and vice versa.
• B) Excited atoms must be at the top of the laser tube.
• C) Excited atoms must be at the bottom of the laser tube.
• D) More atoms are in the higher-energy state than the lower-energy state.
• E) More atoms are in the lower-energy state than the higher-energy state.

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