# Generating Laser

The above left is a three-level laser energy diagram, where $$E_1 < E_2 < E_3$$. Which of following explanations is NOT correct?

a) Level $$2$$ is a metastable state.

b) Electrons stay longer at $$E_2$$ than at $$E_3$$.

c) There is no electron that shows a spontaneous transition from $$E_2$$ to $$E_1$$.

d) If a laser beam can be generated constantly, the electron population in level $$2$$ must be larger than the electron population in level $$1.$$

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