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。
2
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。
3
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.