Franck-Hertz Experiment

http://oak.cats.ohiou.edu/~piccard/radnotes/states.html

Figure 2: Simplified plot of electron kinetic energy as a function of position along the trajectory, for two different accelerating potentials. Segments (a) and (b) are shown with Eacc = 0.9 Eo and segments (c) through (f) are shown with Eacc = 1.1 Eo.