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

Raise your hand if you don't if you don't have a ping-pong ball yet.

这样就可以算,背散射的概率了。

麻省理工公开课 - 化学原理课程节选