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  • To make a laser, all you need to do is give a big collection of atoms enough energy so they're excited and ready to emit light.

    要做出雷射,你所需要的就是給一大群原子足夠的能量

  • Once one of them spontaneously emits a photon, it'll stimulate some of the others to do so, and you get a nice cascade of illumination.

    讓它們激發而足夠產生光。當其中一個原子自發地放產生一個光子,它會刺激其他原子一起產生,然後你就會得到一層好的光

  • But instead of letting all the light escape, it's more powerful to trap it between two mirrors and let it to bounce back and forth through the atoms.

    但是比讓所有的光逸散有用的是,用兩面鏡子把光子困住

  • All that passing light will stimulate them to emit even more light, and as long as you keep on re-exciting the atoms, they're happy to go on emitting light forever.

    且讓它在原子裡來回彈跳。所有通過原子的光會刺激它們產生更多的光,而且只要你持續刺激原子,它們會持續發光直到永遠。

  • But why do the atoms emit light just because another photon passes by?

    但是為什麼原子放出光僅僅只因為有光子通過? 這其實相當

  • It's actually pretty simple.

  • Imagine flipping two coins: they can either be in the same state,or in different states., but photons aren't like coins - no matter how hard you try, you can't tell one apart from another.

    想像一下擲兩個硬幣:它們可以在同一面(同一狀態), 或是不同面(不同狀態)。但是光子不像硬幣,不論你怎麼試,你都不能分辨這兩個光子。

  • So in a "photon-flipping" experiment, that means there's only one way for them to be in different states but two ways for them to be in the same state.

    所以"擲光子"的實驗代表只有一種情況讓它們處於

  • So they're more likely to be in the same state, and in general, this implies that photons always want to be like other photons - to have the same phase, polarization, and go in the same direction.

    不同的狀態;兩種情況在同一狀態。所以光子比較有可能處於同一狀態之下,一般來說,這表示光子總是希望成為其他的光子 來擁有相同的相位,極化方向,以及相同的行進方向。

  • And what's more amazing is that if a solitary photon passes by an excited atom that could emit another photon, there's a good chance it will emit one because the two photons want be together - even before the second one exists.

    更驚人的是,如果一個單獨的光子穿過一個可能會產生光子的激發態原子,這樣很有可能會使它真的產生光子,因為光子傾向於在一起,即使第二個光子還沒存在。

  • So once you have all these friendly photons bouncing around between the mirrors, you can just open up a little hole at the end and let out a blinding stream of coherent light - a laser beam.

    所以只要你有這些在鏡子之間彈跳的光子,最後你就可以只開一個小洞,一束同調光就會出來:雷射光

  • To see lasers in action, check out this sweet episode of "Smarter Every Day" showing a laser you can stick your hand inside!

    要實際看雷射光的話,看看"Smarter Every Day"的其中一集,

  • They also have a bunch of other cool science videos.

    你可以把手固定在雷射裡面!這個節目還有很多其他很酷的科學影片。

To make a laser, all you need to do is give a big collection of atoms enough energy so they're excited and ready to emit light.

要做出雷射,你所需要的就是給一大群原子足夠的能量

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