PSCI 1030 ONLINE: LAB 7 Atomic and Nuclear Physics
PSCI 1030 Online Lab 7 Atomic & Nuclear Physics
INTRODUCTION
The purpose of this lab is to:
1) Visualize different models of the hydrogen atom; explain the similarities for each model and what experimental predictions each model makes.
2) To be able to explain how the photoelectric effect experiment works and why a photon model of light is necessary to explain the results.
You will investigate these phenomena and concepts through a series of simulations. Read over the entire lab procedure below, then complete each task and record your findings in the data section at the end of the lab.
Upon completion, save this document as a PDF with your name in the filename in the form “Yournamehere-atomic.pdf” and upload to the assignment box on online campus.
PROCEDURE
A. Rutherford Scattering via PhET Simulation
a. For this part, go to the following link: Rutherford Scattering PHET simulation and click download to save simulation. The download will save a HTML5 webpage, click to open it. (https://phet.colorado.edu/en/simulation/rutherford-scattering)
b. This simulation lets us model the experimental behavior of two different proposed atomic models: The plum-pudding model and the Rutherford atomic model.
c. First select “Plum Pudding Atom”.
d. Turn on the simulation by clicking the “Alpha Particle” source on the left side of the simulation. This simulates firing a collection of alpha particles at a plum-pudding like model of the atom.
e. Observe the path of the alpha particles and describe your observations on the data sheet.
f. Try changing the energy of the incoming alpha particles. Does changing the energy change the paths of the alpha particles through the plum-pudding model? Answer this question on the data sheet.
g. On the bottom of the webpage, click Rutherford Atom to view a simulation of firing alpha particles at the Rutherford Model atom. Select the multi-atom simulation indicated by the icon.
h. Turn on the simulation by clicking the “Alpha Particle” source on the left side of the simulation.
i. Describe the observed paths of the alpha particles on the data sheet. How are these paths different than the plum-pudding model? Explain how this difference would show up in an experiment.
j. Vary the number of protons, neutrons, and alpha particle energy. Record at least two observations on the data sheet.
B. The Photoelectric Effect via PhET Simulation
a. For this part, go to the following link: Photoelectric PHET simulation and click download to save the simulation. The download will save a java application. Click it to launch. (If you are asked to allow statistical reporting go ahead and allow it and launch the simulation). (https://phet.colorado.edu/en/simulation/legacy/photoelectric)
b. This simulation lets us model the phenomena of the photoelectric effect.
c. First, turn on each of the graphs (on the right) by checking the corresponding box for:
a. Current vs battery voltage
b. Current vs light intensity
c. Electron energy vs light frequency
d. Next, set the intensity of the source to 50% and the wavelength to 400nm (you can either enter a number or drag the slider as indicated). Make sure “Show only highest energy electrons is checked” to simplify things to start.
e. You should see the simulation ejecting electrons that travel from the left to the right plate. Predict which of the following changes could increase the maximum initial energy of the ejected electrons on the data sheet.
a. Increasing/Decreasing the intensity of the light beam
b. Increasing/Decreasing the wavelength of light
c. Increasing/Decreasing the frequency of light
d. Increasing/Decreasing the voltage of the battery
!
Remember: the wavelength and frequency of light are related!
f. Test your predictions. Describe your observations on the data sheet.
g. Uncheck “Show only highest energy electrons”. Select a different metal. Vary the intensity, wavelength of light, and battery voltage again. Answer the corresponding questions on the data sheet. Sketch the graphs and explain.
LAB 7 Atomic & Nuclear Physics Data Sheet
Name:
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Date:
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A. Rutherford Scattering via PhET Simulation
1. Describe your observations of the “Plum-pudding model.” How do the positively-charged alpha particles move through the material?
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2. What does changing the energy of the alpha particle do to the speed of the incoming alpha particle? Does this change the observed path of the incoming alpha particles through the plum-pudding model?
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3. Describe your observations of the Rutherford atomic model. How do the positively charged alpha particles move through the material?
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4. Based on your answers to Questions 1&3, how is the Rutherford atomic model different than the plum-pudding model? How would this show up in an experiment?
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5. Describe at least two other findings from varying the number of protons or neutrons in the material and/or the energy of the incoming alpha particles.
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B. The Photoelectric Effect via PhET Simulation
1. Predict which of the described changes in the procedure will increase the maximum initial energy of the ejected electrons.
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2. For light of wavelength 400nm, what is the frequency? Hint: The speed of a light wave is 3.00 x 108 m/s.
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3. Vary the intensity of the light beam, the wavelength of the light, and the voltage of the battery. Which change(s) affected the maximum energy of the ejected electrons?
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4. Select a different metal: Click here to enter text.
5. At what wavelength is it first possible to remove electrons?
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6. What does changing the intensity of the light do?
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