The Photoelectric Effect
filtered out from the light of a mercury lamp. This light strikes the cathode (C) of a photoelectric cell and causes the emission of
electrons (or not). In order to find the maximal kinetic energy of the ejected electrons it is necessary to enlarge a retarding voltage by
means of a potentiometer connection so much that no more electrons arrive at the anode (A). The blue coloured meter indicates the size
of this retarding voltage. You can see from the red coloured meter whether electrons reach the anode.