So, that can be a little bit confusing for us to think about, and when it's a very good question you might, in fact, say well, maybe there's not zero probability here, maybe it's just this teeny, teeny, tiny number, and in fact, sometimes an electron can get through, it's just very low probability so that's why we never really see it.

这想起来有点令人困惑，你们可能会说也许，这里的概率并不是严格的为零，而是非常非常小，所以有时电子就可以穿过去，这是个,很好的想法。

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I'll give you some examples so it's less confusing.

下面我们用几个例子来消除你的困惑。

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