To answer the following questions, you should use the PhET ...



Answers to Photoelectric Effect AVP Simulation ReviewLearning Goals: To be able to explain how the photoelectric effect limits the efficiency of solar cells. To answer the following questions, you should use the link provided in Module 5 to access the Photoelectric Effect simulation.As you’ve learned from the reading, to understand why solar cells have such a low efficiency in converting solar energy into electrical energy, we have to understand the nature of matter itself. PrepareBefore beginning the simulation, first make sure you understand these basic properties of the atom and the electron.In an atom with one electron, which of the following statements are trueThe total energy of the electron is due to the speed of the electron as it moves around the nucleus of the atom.The total energy of the electron is due to the speed of the electron and its distance from the nucleus.The electron can be found at any distance from the nucleusThe electron can only be found at certain distances from the nucleus.The electron can move farther from the nucleus if it loses energyThe electron can move farther from the nucleus if it absorbs energy.The electron can gain energy by emitting electromagnetic radiation (light).The electron can gain energy by absorbing electromagnetic radiation (light).The energy stored in light is related to its perceived color.Infrared light is more energetic than red light.Red light is more energetic than blue light.InteractionNow open the simulation and use the sliders to create the following situations. Then, answer the questions for each situation described below.2. (Suppose you set up the experiment so that the plate is ejecting electrons. Predict which of the following changes to the experiment could increase the maximum initial kinetic energy of the ejected electrons. (Select all that apply) Then test your prediction. A. Increasing the intensity of the light beam B. Decreasing the intensity of the light beam C. Increasing the wavelength of light D. Decreasing the wavelength of light 3. Suppose now you set up the experiment so that the light intensity is non-zero but the plate is NOT ejecting electrons. Predict which of the following changes to the experiment could make the plate start ejecting electrons and therefore create an electrical current? (Select all that apply) Then test your prediction. A. Increasing the intensity of the light beam B. Decreasing the intensity of the light beam C. Increasing the wavelength of light D. Decreasing the wavelength of light 4. What causes the electrons to be ejected from the left plate in this simulation? A. The force exerted on the electrons by the battery B. The beam of light shining on the plate C. Both A and B. D. Neither A nor B. Evaluation5. Change the target material from Sodium to Copper using the drop-down box. Describe the type of light necessary to eject the photoelectrons from the copper surface. Can we see this light?6. Which of the available materials are responsive to the largest number of wavelengths? Use the answer to this question to explain how to improve the efficiency of solar cells.The best material for constructing solar cells would be a material where the electrons in the atom do not require much energy to eject photoelectrons. As such, this material will respond to photons with larger wavelengths and more of the electromagnetic radiation will produce a current in the cell.7. (essays) These essays are designed to help you understand how the observations from the photoelectric effect experiment lead to and make sense only with a photon model of light. The following are some key experiments from the photoelectric effect. For each, explain what you observe what conclusions you can draw about light and why, and how does the observation help you understand why the efficiency of a solar cell which uses the photoelectric effect is low. Remember, efficiency is described as how much of the available energy is converted to electrical energy.a. (essay) Light is shining on a metal and electrons are being emitted. You turn the intensity down very, very low. 1. The electrons are emitted but at a very slow rate.2. Intensity is a measure of the number of photons in a beam of light. If each photon carries the same energy, then fewer photons will cause fewer photoelectrons to be ejected.3. A low intensity means fewer electrons traveling in the circuit, leading to a smaller current. On bright sunny days where clouds don’t filter out photons, the solar cell will operate at maximum output. b. (essay) Light is shining on a metal plate and electrons are being emitted. Without changing the intensity, you make the wavelength longer and longer. The electrons are emitted at a steady rate but with less speed until no electrons are ejected.The photons for light with small wavelengths pack a lot of energy which is transferred to the electron. If this energy is enough to eject the electron, then what is left over is transferred to the speed of the electron. As the wavelength gets longer, the amount of energy left over after its ejection decreases and therefore its speed decreases until the energy in the longer wavelength photons is not enough to eject the electrons.Not all of the light from the sun is absorbed by the electron to create photoelectrons. There is a large range of sunlight that will never be used to create current in a solar cell no matter how bright the sun is in the sky, and this is why solar cells are not high in efficiency because these large wavelength photons are ignored by the solar cell.SummaryIn the photoelectric effect, each atom on the surface of the metal tightly binds their electrons to the nucleus. If light photons are energetic enough, each photon will transfer its energy to the electron to both (1) remove the electron from the bounds of the nucleus, and (2) if any energy is left over, the energy is converted to the kinetic energy and is therefore the speed of the electron. The speed of the electrons across the gap is directly related to the electrical current in the circuit. ................
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