This diagram shows two energy levels in an atom. The lower level is "full" because it already has an electron with spin up and another with spin down. Therefore, a third electron must go into the higher energy level. What law or principle explains why?

A) the exclusion principle
B) the uncertainty principle
C) the law of conservation of angular momentum
D) the law of conservation of energy


A) the exclusion principle

Physics & Space Science

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When an object is placed 118 cm from a thin diverging lens, its image is found to be 59 cm from the lens. The lens is removed, and replaced by a thin converging lens whose focal length has the same magnitude as the diverging lens

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