Concept Questions for the Photoelectric Effect with Interactive Simulation
This activity has benefited from input through a review and suggestion process.
This activity has benefited from input from faculty educators beyond the author through a review and suggestion process as a part of an activity development workshop. Workshop participants were provided with a set of criteria against which they evaluated each others' activities. For information about the criteria used for this review, see http://serc.carleton.edu/sp/compadre/devactivities/reviewcriteria.html.
This page first made public: Jul 30, 2007
This material is replicated on a number of sites as part of the SERC Pedagogic Service Project
- Students should understand the relationship between photon wavelength and energy and its relation to the kinetic energy of the photoelectrons.
- They should also understand how the stopping potential is used to determine the electrons' kinetic energy.
Context for Use
Description and Teaching Materials
The simulation is embedded within a Spanish Language Page by Angel Franco Garcia. It can be run directly from http://www.sc.ehu.es/sbweb/fisica/cuantica/fotoelectrico/fotoelectrico.htm#Actividades%20a%20realizar.
Teaching Notes and Tips
Using the SimulationBefore presenting the question, students should be allowed to see the simulation operate. They should also be given a minimal verbal description of the process. An example: The battery in this system pulls some electrons from the plate on the left and places them on the other plate. The plates now have equal and opposite charges, and there is an electric field in the region between them that points to the right. When the Foton (photon) button is pressed, the Lampara (lamp) emits a photon toward the left plate, where it is absorbed by an electron that is then ejected into the region between the plates. Since the captions are in Spanish, extra care is needed to be certain students are clear on the names and functions of any components in the simulation you are using.
Notes about Question 1
B is the correct choice. Increasing the potential difference increases the field strength which results in a larger retarding force on the electron.
Students who choose A may think that the potential is causing the electron to move across the gap rather than opposing it. Those choosing C may not realize that the electric field strength is determined by the potential difference.
Notes about Question 2
A is the correct choice. Decreasing wavelength increases frequency so the photon imparts more kinetic energy to the electric.
Students who choose B may be confused by the inverse relationship between energy and wavelength as compared to energy and frequency. Those who choose C may not realize that the source of the electron's energy is the photon it absorbs.