So, now we can talk about it in different terms, Ei for example, talking about e sub i, which is the incident energy or the energy of the light that comes in, or talking about work function here, and that's just another way to say threshold energy.

现在我们可以从不同的方面,来谈论它了，举例来说，它是入射能量或者进来的光的能量,或者谈论这里的功函数，它是另一种描述临界能量的方式。

麻省理工公开课 - 化学原理课程节选