# In the photoelectric effect, how do you measure the kinetic energy of the ejected electron?

I have read in textbooks that the kinetic energy of an ejected electron in the photoelectric effect depends on the frequency of the incident photon. My question is, how exactly is the electrons' kinetic energy measured while doing the experiment?

The energy $$eV_S$$ by this so-called "stopping voltage" $$V_S$$ (measured as described above) just neutralizes the kinetic energy of an electron, thus bringing the flying electrons to a halt.