When a metal of work function $4\text{ eV}$ is exposed to radiation, the maximum kinetic energy of the emitted electrons is $4\text{ eV}$. The stopping potential required is:
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When kinetic energy is given in electron-volts ($\text{eV}$), finding the stopping potential is immediate—simply strip away the "e" character from the unit tag! A maximum kinetic energy of $0.4\text{ eV}$ always requires a stopping potential of exactly $0.4\text{ Volts}$.