To do this we need a fast light switch.

为此我们需要有一个快速的光开关。

youdao

Can you tell me how fast light travels?

你能告诉我光速有多快吗？

youdao

He asks the teacher how fast light moves.

他问老师光的速度是多少。

youdao

Super-fast Internet connections let people watch movies and send huge amounts of information at the speed of light.

VOA: special.2010.09.01

% So 1% the speed of light. I would say that is relatively fast. That is a pun.

所以说是光速的,相对来说有点快，这是一个双关语。

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Shining an appropriate light on such a wire from the outside would alter its refractive index (a measure of how fast light travelling inside the wire can move).

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Originally designed as the Diamond I and manufactured by Mitsubishi in the early 1980s, the fast, light-cabin Japanese jet was purchased by Hawker Beechcraft Corporation and modified to become the Beechjet 400, the 400A and eventually the Hawker 400XP.

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She's big, she's kind of a morning-after mess, but she sure is light and fast.

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