Suppose there is a potential difference between the metal that ejects the electrons and the detection device, such that the detector is at a lower potential than the metal. The electrons slow down as they go from higher to lower electric potential; since they must overcome this potential difference to reach the detector, this potential is known as the stopping potential. To reach the detector, the initial kinetic energy of an ejected electron must be greater than or equal to the amount of energy it will lose by moving through the potential difference.

If there is a potential difference V between the metal and the detector, what is the minimum energy Emin that an electron must have so that it will reach the detector?

Express your answer in terms of V and the magnitude of the charge on the electron, e .