The photoelectric effect is widely taught in schools and institutions. It is common knowledge that in order for photoelectrons to be emitted, the energy of the incoming photons must be greater than the work function of the irradiated metal (i.e. hv greater than [phi][subscript emitter]). However, what may not be as commonly known is that the "[phi]" in Einstein's photoelectric equation (eV[subscript s] = hv - [phi]) is often implicitly and mistakenly taken as the work function of the emitter (or anode) rather than that of the collector (or cathode). This paper provides experimental evidence for the more correct but the non-intuitive form of the photoelectric equation eV[subscript s] = hv - [phi][subscript collector], which can also be theoretically derived by taking into account the contact potential difference between the electrodes. This equation is shown experimentally to be invalid for hv less than [phi][subscript emitter] and hv greater than [phi][subscript collector], even though in such a case a positive V[subscript s] (stopping potential) is obtained by the equation, no V[subscript s] is obtainable experimentally. However, the equation is valid for hv less than [phi][subscript collector] and hv greater than [phi][subscript emitter] where a negative V[subscript s] is obtained from the equation, which corresponds to an experimentally observed "starting potential". (Contains 3 figures.)