The photoelectric effect: experimental confirmation concerning a widespread misconception in the theory

Abstract

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. hν > ϕemitter). However, what may not be as commonly known is that the ‘ϕ’ in Einstein's photoelectric equation (eVs = hν − ϕ) 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 eVs = hν − ϕcollector, 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 hν < ϕemitter and hν > ϕcollector, even though in such a case a positive Vs (stopping potential) is obtained by the equation, no Vs is obtainable experimentally. However, the equation is valid for hν < ϕcollector and hν > ϕemitter where a negative Vs is obtained from the equation, which corresponds to an experimentally observed ‘starting potential’.

A Study Investigating the Effect of Treatment Developed by Integrating the 5E and Simulation on Pre-service Science Teachers’ Achievement in Photoelectric Effect

“…In recent years, researchers have focused their attentions to the students' understanding of quantum physics concepts at different school levels (Asikainen & Hirvonen, 2009;De Leone & Oberem, 2004;McKagan, Handley, Perkins, & Wieman, 2009;Steinberg, Oberem, & McDermott, 1996;Yıldız & Büyükkasap, 2011). Photoelectric effect is one of the important quantum physics topics that play a crucial role in understanding the photon model of light (McKagan et al, 2009;Wong et al, 2011). Unfortunately, the previous researches reported that most of the students from different educational levels have serious learning difficulties in understanding the basic aspects of photoelectric effect such as interpreting experimental set-up, predicting experimental results and its' relation to the photon model of light (De Leone & Oberem, 2004;McKagan et al, 2009;Sokolowski, 2013;Steinberg et al, 1996).…”

Discussion for the enhanced understanding of the photoelectric effect

“…However, since the cathode and anode plates are generally made of different materials, the work function f cannot simply be used in the equation, as the work functions of both the two metals must be considered [32,33]. That is, the formula can be satisfied only when the cathode and anode plates are made of the same material.…”

“…Figure 4 shows the I-V characteristics according to the type of metals used for cathode and anode [33]. Zinc and Nickel were chosen as the emitter and collector of electrons, and three different cases are Zn-Zn (h ).…”

The Physics of Health Care: Viewing the U.S. Health‐Care “System” from the Perspective of Quantum Mechanics

“…The photoelectric effect is representative of the finding that shining light on certain materials can eject electrons from that material (Wong et al, ). The minimum amount of energy necessary to eject electrons from a particular material is referred to as the work function.…”