It's not going to be a backscatter event if your ping-pong ball hits the frame or these strings, or the top part.

打到原子核了就是背散射,如果打到框上。

麻省理工公开课 - 化学原理课程节选

So, it'll be considered a backscatter event if your ping-pong ball hits one of the nuclei.

什么情况是背散射,如果你们的乒乓球。

麻省理工公开课 - 化学原理课程节选

Let me explain to you what constitutes a backscatter event.

先不要扔，让我解释一下。

麻省理工公开课 - 化学原理课程节选

But in our case, the probability of backscattering is going to be the number of balls that backscatter, and that's going to be divided by the total number of ping-pong balls.

用20除以132000，但现在背散射,的概率是被散射回来的小球，除以总的小球数,你们记得。

麻省理工公开课 - 化学原理课程节选

We know we need to divide by 266, 266 but what we need you to help us with is to figure out this top number here and see how many particles are going to backscatter. So if the TAs can come up and quickly hand out 1 particle to everyone.

知道背散射的概率就可以了，我们知道要除以,但还需要你们来搞清楚,分子上的数是多少，有多少个发生背散射的粒子,助教们请过来,把这些球分给同学们。

麻省理工公开课 - 化学原理课程节选