In a photocell, ultraviolet (UV) light provides enough energy to some electrons in barium metal to eject them from a surface at high speed. See Fig. 17-33. To measure the maximum energy of the electrons, another plate above the barium surface is kept at a negative enough potential that the emitted electrons are slowed down and stopped, and return to the barium surface. If the plate voltage is €“3.02V (compared to the barium) when the fastest electrons are stopped, what was the speed of these electrons when they were emitted?

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V--3.02 V UV light Barium