The photoelectric effect refers to a phenomenon in which a high energy photon ejects an electron from a metal surface (Lvovsky, 2018). The present experiment examined the fundamental physical principles concerning the photoelectric effect. The experiment was divided into four parts including the introduction, the methods, the results and discussion, and the conclusion sections. The introduction focuses on the underlying theoretical principles concerning the photoelectric effect, the experiment process is under the methods section, and the observed principles will be addressed in the results and discussion part. The final part confirms the identified principles in the introduction.
Introduction
The experiment focused on the photoelectric effect as the primary physical principle. Quantum physics studies how particles at the subatomic or atomic levels interact. Greek philosophers introduced the quantization principle during the fifth century BCE after arguing for the presence of indivisible small particles that they called atomos (Wolfson 532). When light strikes a metal surface and ejects electrons it causes the photoelectric effect. The ejected electrons flow as current after the application of an electric field (Lvovsky, 2018). The setup required to perform a photoelectric experiment involves organizing apparatuses to observe electron emissions using different light wavelengths. These apparatuses include cathode and anode plates, a vacuum tube, a battery, an ammeter, and a source of light. The experimental setup includes placing the anode and the cathode inside the vacuum tube, using the battery to connect the anode and the cathode plates to complete a circuit, and observing how the current changes using the ammeter. The light source offers varying light wavelengths and intensities to the cathode plate.
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The first equation demonstrates the inverse relationship between frequency and wavelength (Kumar, 2018).
Speed of light (c) =3x10^8 m/s. The second equation is based on Planck’s formula,
(Kumar, 2018)
It shows that the atomic vibration energy is proportional to the oscillation frequency in which h refers to Planck’s constant (6.626x10^-34 J s). Einstein extended Planck’s quantum idea in 1905 by including light (Wolfson 538). Combining the two equations gives the third equation referred to as the quantum of electromagnetic wave energy equation (Kumar, 2018),
Adequately energized photons (light bundles) can eject electrons from a metal surface. Work function or the energy barrier refers to the required energy to eject the electrons. Computing the threshold frequency of the metal gives the metal’s work function (Lvovsky, 2018). The threshold frequency refers to the point when a photon has sufficient energy to eject an electron from a surface. The work function formula (Kumar, 2018) is given by,
Methods
The experiment used the Photoelectric Effect (1.10) lab simulation. Opening the simulation resulted in the displaying of apparatuses. These apparatuses included a cathode and anode inside a vacuum tube, a light source, a battery, and an ammeter. The light source varied based on its wavelength and intensity. The change of the metal material and the displaying of different graphs depended on the lab’s right side controls. The method involved first selecting the current versus light intensity and electron energy versus light frequency graph boxes. The platinum metal was then selected following a 10 percent adjustment of the light intensity and a slight reduction of the light wavelength above the threshold frequency. Achieving the threshold frequency entailed lowering the wavelength to the point where electrons started being ejected from the cathode plate. Observations including the energy, current, wavelength among others were recorded. The light intensity was then increased slowly until it reached 100 percent in which observations including changes in energy and current and others were recorded. The next step involved resetting the light intensity to 10 percent while lowering the wavelength to above the threshold frequency and recording all observations. This was followed by a slow increase of the light intensity until it reached 100 percent. Observations were recorded.
Results
The experimental results demonstrate that the ejection of electrons from the cathode towards the anode occurred at a 196 nm wavelength. Changing the light intensity to 10 percent led to a negligible change in the current or electron energy. Increasing the intensity to 100 percent did not result in any change in electron energy or current. Electron emission increased and the speed of the electrons towards the anode increased when the intensity reduced to 10 percent while the wavelength reduced to 150 nm. The electron energy reached nearly 2eV while the current shown by the ammeter was 0.033 amps when the intensity remained at 10 percent. The electron energy remained the same (2eV) while the current rose to 0.097 amps when the intensity increased to 30 percent. Raising the intensity to 60 percent led to a current reading of 0.192 amps while the electron energy remained the same (2eV). The current rose to 0.320 amps while the electron energy remained the same (2eV) when the intensity reached 100 percent.
Discussion
The observed results lead to several conclusions. While electrons moved between the plates at the threshold frequency, negligible electron energy and current could be observed. Lowering the wavelength of the incident light increased the frequency, which led to a high number of electron emission. Increasing the frequency also increased the energy of the emitted electrons. Besides, changing the wavelength also led to changes in electron energy and current while changing the light intensity led to a change in current only. The current was observed to be proportional to the light intensity. A linear increase in the current vs light intensity graph was observed when the wavelength was 150 nm.
Conclusion
The experiment investigated the photoelectric effect in which the results show that the threshold frequency depends on the type of metal. The number of ejected electrons increases when the frequency of light increases. The intensity of light was also observed to affect the kinetic energy of the electrons.
References
Kumar, A. (2018). Fundamentals of quantum mechanics . Cambridge University Press.
Lvovsky, A. I. (2018). Quantum physics: An introduction based on photons . Springer
Wolfson, R. (2010). Essential College Physics . Pearson. Volume 2. Chapter 23
