And then I could put a couple of plates and I could raster the beam so that when I am looking here,the beam goes back and forth about 80 times a second.

然后我放了两个感光片,我可以检测到光束所以,当我观察时,电子束以每秒80次的速度来来回回了。

麻省理工公开课 - 固态化学导论课程节选

But, from this moment forth, cell phone goes off, you're out. You leave the room, OK? And, Lord help you if a cell phone goes off during an exam because those things have text messaging capabilities.

但是，从这一刻开始，手机响的话，你们就出去，你们就离开教室，好吗，上帝保佑你的手机不要在考试期间响起,因为它们有发短信的功能。

麻省理工公开课 - 固态化学导论课程节选

And then he goes back to hell and then back up to heaven -goes back and forth between these two rhythmically very different concepts.

然后它回到了地狱,接着又升到了天堂,在这两种节奏非常不同的概念之间,来回往复

耶鲁公开课 - 聆听音乐课程节选

So the bar just goes back and forth.

这个木杆可以来回移动

耶鲁公开课 - 心理学导论课程节选