Therefore, a level of 70 per cent of initial light level could be considered a threshold of useful life for general lighting.

因此，初始亮度的70%可以被当做普通照明有用时间的一个门槛。

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You turn the door knob, step over the door threshold and find this beautiful room that just feels like a soft glowing light.

你转动门把手，跨过门槛进入门内，发现这个漂亮的房间感觉起来有些像是用柔和辉光构建的。

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So, for example, we were talking about a threshold frequency as in a minimum frequency of light that you need in order to eject an electron from a metal surface.

举个例子来说，我们谈论的临界频率是，光从金属表面逐出一个电子，所需的最小频率。

youdao

So, for example, we were talking about a threshold frequency as in a minimum frequency of light that you need in order to eject an electron from a metal surface.

举个例子来说，我们谈论的临界频率是,光从金属表面逐出一个电子,所需的最小频率。

麻省理工公开课 - 化学原理课程节选

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