PhET (Physics Education Technology) Virtual Laboratory
as Physics Learning Media about Factors that Influence
the Number of Emitted Electrons in Photoelectric Effect
Satriya Ary Hapsara, Debora Natalia Sudjito, Diane Noviandini
Department of Physics Education, Faculty of Science and Mathematics, Universitas Kristen Satya Wacana, Salatiga, Indonesia
Abstract
Experiments have a very important role in physics, because a scientific phenome-non could be investigated and understood through it. A photoelectric effect is a phenomenon that explains the nature of light and the fundamental of quantum me-chanics. The lower cognitive level of undergraduate students about the photoelectric effect is caused by the limitation of apparatus in the real laboratory. This study de-scribes the exploration of the photoelectric effect simulation on PhET virtual la-boratory (Physics Education Technology) about factors that influence the number of emitted electrons in the photoelectric effect. The investigated variables are voltage, metal material, light intensity, and light wavelength. The current is used to indicate the number of emitted electrons. Those are accommodated in the photoelectric ef-fect simulation on PhET so that four experiments could be done i.e. : the efef-fect of voltage to current, the effect of metal material to current, the effect of light intensity to current, and the effect of light wavelength to current. Based on the exploration of PhET simulation, the result showed some factors that influence the number of emit-ted electrons in the photoelectric effect such as metal material, light intensity, and light wavelength. This is consistent to references, thus photoelectric effect simula-tion on PhET can be used in the learning process to investigate factors that influ-ence the number of emitted electrons in the photoelectric effect.
Keywords: PhET (Physics Education Technology) simulation, photoelectric effect, emitted electrons
1 INTRODUCTION
A photoelectric effect is a phenomenon of quantum mechanics that explains the na-ture of light. It is able to help students to understand the nature of light as a photon. A research shows that there were serious difficulties for students to understand it even in the the most fundamental aspect of the photoelectric effect. It is because the
alterna-tive for doing modern physics experiment activities, including the photoelectric effect. Research studies have also indicated that visualization of this phenomenon through computer simulations can contribute to develop students’ understanding of physics concepts at the molecular level by attaching mental images to these concepts.
According to Jr, Romualdo S Silva., 2015, animations are able to refine a concept and relate what we have seen to what we have heard and understood. Therefore, using vir-tual laboratory for doing photoelectric ef-fect experiment activity is relevant to improve students’ understanding about its concept, as Ajredini, Fadil., et al 2013 and Musafa Baser., et al 2010 stated that there was no significance difference between students’ knowledge by doing experiment activity on virtual laboratory and traditional laboratory. This study aims to describe the exploration of the photoelectric effect simu-lation on PhET virtual laboratory (Physics Education Technology) about factors that influence the number of emitted electrons in the photoelectric effect.
2 METHODS
This study is a qualitative research that describes the exploration of the photoelec-tric effect simulation on PhET virtual la-boratory (Physics Education Technology) in order to investigate factors that influence the number of emitted electrons in the pho-toelectric effect. Some experiments have been done by students in order to comprehend the factors that influence the number of emitted electrons in photoelec-tric effect were explored in this study.
There were four activities which had been done, i.e. : (1) investigating the effect of voltage to current, (2) investigating the effect of metal material to current, (3) investigating the effect of light intensity to current, and (4) investigating the effect of light wavelength to current. On each activity, all variables would be determined to guide the students to find factors that in-fluence the number of emitted electrons in the photoelectric effect. The results in each activity would be compared to the references to ensure the consistency among the experiments results using virtual laboratory PhET towards the prevailing theory.
3 RESULT
To investigate factors that influence the number of emitted electrons in the photoelec-tric effect, some variables such as voltage, metal material, light intensity, and light wavelength could be examined using the photoelectric effect simulation on PhET virtual laboratory. In this case, current can be used to indicate the number of emitted elec-trons.
Activity 1. The Effect of Voltage Towards the Number of Emitted Electrons.
wave-length were determined as the controlled variables.
The magnitude of voltage (V) was changed gradually from 0 volt to 8 volt. The chosen metal material was Sodium, light intensity (I) was 75%, and light wavelength (λ) was 180 nm. The measurement results of current (i) were recorded. Based on the PhET simulation,it was found that the number of electric current is always constant. To ensure the experiment results, we related it with Ohm’s Law by making the “current vs bat-tery voltage” graph in PhET to see the relationship of voltage towards emitted electrons (current) as shown in Figure 1. This graph showed that Ohm’s Law is invalid on the photoelectric effect phenomenon. Thus, the magnitude of voltage did not affect the number of emitted electrons (current).
Figure 1. The emitted electrons (current) towards voltage graph at λ=180 nm, metal material = Sodium,I=75%, andV= 0-8V.
Activity 2. The Effect of Metal Material Towards the Number of Emitted Electrons.
To investigate the effect of the metal material towards the number of emitted electrons, the metal material was determined as the dependent variable; the current was determined as the independent variable; the voltage, the light intensity, and the light
wavelength was determined as the controlled variables. One by one, the metal material was changed to Sodium, Zinc, Copper, Platinum, and Calsium. The chosen light intensity (I) was 75% and light wavelength (λ) was 180 nm to measure the current produces on each metal material changes.The measurement results of electri-cal current (i) were recorded on Table 1.
Table 1.The experiment results of the effect of metal material towards the number of current (emitted electrons).
Metal Materials
Emitted
Electrons Current (A) Emerge None
Sodium √ 1,191
Zinc √ 0,499
Copper √ 0,356
Platinum √ 0,026
Calsium √ 1,184
Based on the data in Table 1, all of the metal materials emerged electrons and the current was different for each metal material. Thus, the metal material affected the number of emitted electrons (current).
Activity 3. The Effect of Light Intensity Towards the Number of Emitted Electrons.
wavelength was determined as the controlled variables.
Using the Sodium material, the light wavelength (λ) of 180 nm, and the voltage of 0 V, the light intensity (I) was changed gradually from 0% to 100% with 10% interval. The 10% interval is not a must. It could be 1%, 5%, or 15% etc as long as its change was constant. The measurement results of current (i) were recorded. Based on the PhET simulation, it was found that each change on light intensity produced different current. It was supported with “current vs lightintensity”graph as shown in Figure 2.
Figure 2. The light intensity towards the number of emitted electrons graph atλ=180 nm, metal material = Sodium,I=0-100%.
According to the above graph, the greater magnitude of light intensity, the greater the current, the greater the number of emitted electrons. Thus, the light intensity affected the number of emitted electrons (current).
Activity 4. The Effect of Light Wavelength Towards the Number of Emitted Electrons.
To investigate the effect of the light wavelength towards the number of emitted electrons, the light wavelength was determined as the dependent variable; the
current was determined as the independent variable; the voltage, the metal material, and the light intensity was determined as the controlled variables.
Using the Sodium material, the light intensity of 75%, and the voltage of 0 V, the light wavelength (λ) was changed gradually from 200 nm to 850 nm with 50 nm interval. The measurement results of current (i) were recorded as shown in Table 2.
Table 2.The experiment results of the effect of the light wavelength towards the number of current (emitted electrons).
Light Wavelength
(nm)
Emitted
Electrons Current (A) Emerge None
200 √ 1,258
250 √ 0,731
300 √ 0,417
… …
800 √ 0,000
850 √ 0,000
Based on the data in Table 2, the greater magnitude of light wavelength, the smaller the current, the smaller the number of emitted electrons. Thus, the light wavelength affected the number of emitted electrons (current).
learning process to investigate factors that influence the number of emitted electrons in the photoelectric effect.
4 CONCLUSION
The exploration of the photoelectric effect simulation on PhET showed that factors in-fluencing the number of emitted electrons in the photoelectric effect are the metal materi-al, the light intensity, and the light wave-length which is consistent to the prevailing theory. Thus, the photoelectric effect simu-lation on PhET can be used in physics learn-ing to investigate factors that influence the number of emitted electrons in the photoe-lectric effect.
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