So, if instead you put your particle somewhere down here on the electric field, or on the wave, the electric field will now be in the other direction so your particle will be pushed the other way.

还有方向，所以如果,你把粒子放在这下面，电场的方向相反,粒子会朝另一个方向运动。

麻省理工公开课 - 化学原理课程节选