Experimental Confirmation Concerning a Widespread Misconception

Title The Photoelectric consequence Experimental confirmation c one timerning a widespread Misconception in the Theory Gao Shenghan 1, Huan Yan Qi 1, Wang Xuezhou 1, Darren Wong 2, Paul Lee 2 and Foong See Kit 2 1 Raffles Institution, One Raffles Institution Lane, Singapore 575954 2 infixed Sciences and Science Education, National Institute of Education, Nanyang Technological University, Singapore 637616 Abstract The photoelectrical stamp is a well-known and widely taught field in some schools and institutions, yet it has been shown through theoretical arguments that there is a common erroneous belief in the theory in which this topic is learnt and taught.The common theory is that the postcode of the incoming photons must be greater than the bend function of the emitter, and to a fault that the deflection in the midst of the verve of the photon and the work function of the emitter must be greater than the potency utilise between the emitter and accumulator register mul tiplied by the elementary charge. This paper provides experimental evidence for the correct interpretation of the photoelectric effect in order to correct the misconception.In this paper, it was experiment individually(prenominal)y determined that 2 the work functions of the emitter and the accumulator register metallic elements must be taken into account in order for a current to be detected, contrary to conventional theory. fundament The photoelectric effect is the phenomenon in which electrons are liberated from matter as a result of electromagnetic radiation being shone onto it. Generally, the phenomenon is only investigated in metals as they require lower null from the radiation. The photoelectric effect was original discovered by Heinrich Hertz in 1887 and was explained by Albert encephalon in 1905.Einsteins model quantized light as photons, each with cypher E=h? where h is the Plancks constant and ? is the frequency. Einstein in like manner introduced the work func tion ? of a material, defined as the minimum sum up of energy needed in order to liberate an electron from the material. by dint of this model, the characteristic photoelectric equation eVs=h? -? can be derived where Vs is the taenia potential drop. Eisnteins report and relations of the photoelectric effect, shown below, has been taught in many schools all around the world today and is widely known. Theory In this plane section we present the derivation of the photoelectric equation eVs=h? ?. From the definition of ? , it follows that once an electron has been liberated, it has a maximum possible kinetic energy of h? -?. This also implies that h? ? for a liberation of electron. When an orthogonal potency V is employ across the metals, there is a potential remnant between the plates and thus when the electron needs KEeV in order to to reach the collector plate. Combining the two relations, we get h? -? eV. In the equality case, we shout the voltage Vs, which is the is the m inimum amount of voltage needed to be applied such that no current is recorded. Conventional understanding of the photoelectric effect Alternative understanding of the photoelectric effect The preceding(prenominal) section uses the work function ? e referred to that of the emitter material, even when the emitter and collector are made of divergent materials. However, this is incorrect, and the derivation is shown below When an electron is just emitted from come out of the closet of the emitter, it has potential energy ? e above the ground energy state. Conversely, when an electron is just emitted from surface of the collector, it has potential energy ? c. Hence, if ? e c, we note that there will be a potential energy difference of ? c-? e, even if there is no impertinent voltage applied.This is known as the contact potential. ?c ?e ?c-? e authorization energy Emitter Collector Figure 1 Energy diagram without an external voltage ?c ?e ?c-? e Potential Energy Emitter Collector F igure 1 Energy diagram without an external voltage Once a potential difference of V is applied between the two plates, there is an gainal potential energy difference of eV. Collector ?e Potential Energy Emitter ?c ?c-? e+eV eV Figure 2 Energy diagram with an external voltage applied Collector ?e Potential Energy Emitter ?c ?c-? e+eV eV Figure 2 Energy diagram with an external voltage appliedHence, in the process of calculation, the difference in potential energy of the two plates is not eV, further instead ? c-? e+eV. Thus, replacing this into the Einstein equation, we get eVs=h? -? c. Hypothesis The two requirements for a current to be detected in a photoelectric effect experiment are 1. h? ? e 2. h? -? ceV Instead of the commonly-quoted 1. h? ? e 2. h? -? eeV Objective To provide actual experimental confirmation of the proposed model, in addition to the currently-available purely theoretical arguments, in order to determine the correct explanation for the photoelectric effect Ap paratus and methodologyOver mountain The experiment consists of a vacuum bedroom with thin Zn and Ni plates placed close together but not touching. UV light was shone onto one of the metal plates and the resulting voltage between the two plates was measured. The materials of the emitter and the collector were changed, as well as the potential difference applied across the two plates. I-V curves were plotted and the results analysed. Experimental setup A cylindrical vacuum house at was pressure 1. 5? 10-2 mbars was use. The emitter and collector plate were placed in the vacuum chamber and were held up use polycarbonate discs, rods and metal rods.The metal plates were placed with the surfaces parallel to each other at a fixed distance of 1. 0 cm apart. The surfaces of the plates were sandpapered after each trial. The overall setup of the circuit is shown in Figure 8. Crocodile clips were then used to connect the emitter and collector to the external circuit which can be seen in Fi gure 9. A windowpane made of cerulean glass was constructed in order to let UV light enter the chamber (Figure 6). This was align with the metal plates such that the emitter received as much light as possible.A UV light source was placed directly outside the sapphire window and shone UV light onto the emitter plate. The measurements from these two voltmeters will then be used to plot an I-V curve for each of the configurations Zinc-Zinc, Nickel-Nickel, Zinc-Nickel, Nickel-Zinc. In each of the above cases, the emitter is named before the collector. Figure 3 Vacuum chamber 3 4 5 6 Figure 3 Vacuum chamber 3 4 5 6 Figure 6 Sapphire window used to let UV light into the chamber Figure 6 Sapphire window used to let UV light into the chamber Figure 7 UV Light used Figure 7 UV Light used Figure 4 Close-up of polycarbonate disc, rod and metal rodFigure 4 Close-up of polycarbonate disc, rod and metal rod Figure 5 Close-up of the two metal plates Figure 5 Close-up of the two metal plates Figure 8 Overall view of setup Figure 8 Overall view of setup Figure 9 Circuit used for measurement of voltage and current Figure 9 Circuit used for measurement of voltage and current Wangxuezhou Results & Discussion Zn-Zn measurements Figure 10 I-V Graph for the Zn-Zn setup The nonzero photocurrent as measured at 0 V of applied voltage shows that the photon of the UV light has sufficient energy to cause emission of electrons from the Zn plate.Therefore this implies h? ? Zn. In particular, we see that h? -eVstopping? 6. 63? 10-341. 60? 10-193. 00? 108254? 10-9-1. 10 ? 3. 88eV Zn Ni-Ni measurements The results for this setup produced values of zero photocurrent for all possible applied voltages. This mode that the UV photon has less energy than the work function of Ni, in other words, h?