If I went on and told you what the different incident light was, and what the electrons were ejected with, and then you could look up the ionization energy for the particular different elements, you should be able to actually determine exactly which element it is, but just with the information given, we can only narrow it down to these choices here.

如果我继续告诉大家入射光源是什么，出射电子的动能是多少，那么你可以去查一查,以上各个元素的电离能，这样你就应该能确定,这个元素到底是哪个，但是只凭题目中的信息，我们只能把范围缩小至以上几种元素。

麻省理工公开课 - 化学原理课程节选