来自《耶鲁大学开放课程：新生有机化学 第6集 第6集》

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  but how big the actual helix is you get from the spacing of those dots,
  而螺旋的实际大小还要靠光点的间距反映
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  if you know the wavelength and the distance that you're magnifying;
  如果知道了光的波长和光程
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  in the case of the demonstration,
  也就是这里
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  the distance from the slide at the back of the room
  教室后面的幻灯片
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  to the front of the room, for seeing this.
  到前面黑板上的这个图像之间的距离
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  And the spots weaken successively because of wire thickness,
  而因为螺线具有一定的厚度
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  as we just explained, as you go on out.
  成像位置越远 亮点的亮度越低
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  Now, that looks very much like
  这就和富兰克林在1952年得到的
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  Rosalind Franklin's b-DNA photograph from 1952.
  B型DNA的图片很相像了
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  So we see the helix
  我们得到了这个衍射图案
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  and we see how angled the successive turns of the helix are,
  并从X两臂间的角度
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  what the pitch of the helix is,
  得到了螺旋的螺距