Suppose the potential between each dynode in our photomultiplier tube is 80V. From the relationship we found from our last plot, this would mean that two secondary electrons would be emitted for each incident electron at each dynode. Suppose a photon has struck the photocathode of the photomultiplier tube and has emitted the initial photoelectron. What will happen when this electron strikes the first dynode?

The initial electron caused the dynode to emit two secondary electrons. Each of these electrons are accelerated to the second dynode. What will happen when these electrons strike the second dynode?

Each of these electrons produced two more secondary electrons, resulting in a total of four electrons. Each of these electrons is accelerating to the third dynode. How many electrons will there be after these strike the third dynode?

Each electron ejected two secondary electrons, and now there are a total of eight electrons in the photomultiplier tube. All eight are accelerated to the fourth dynode, and each will produce two more secondary electrons. Then there will be 16 electrons, and each of those will produce two secondary electrons at the fifth dynode, totaling 32. At the sixth dynode there will be 64 electrons, 128 at the seventh, and so on.