Wednesday, March 14, 2012

AP Physics:
Exploring Light and Color with Hubble

Learning Objectives
Students will be able to demonstrate their understanding of color addition by creating a color image using three monochromatic Hubble Space Telescope images.

Activity Type
This activity is best used as an introductory project to activate student enthusiasm for learning about light and color. The project instructions will guide students through the process of creating a color astronomical image, which involves principles of color addition for light. 

Assignment Details
  • Visit the project homepage at:
  • Go to Activity 6 and read the introductory instructions.
  • Work through Step 1 of the activity to learn the basics of using ImageJ to view astronomical images.
  • Complete Step 2 of the project to create your own version of the iconic Hubble image, "Pillars of Creation."
  • In Step 3, choose an astronomical object of interest to you and try to create a true color image that accurately depicts the object. Save your final image as a JPEG.
  • Write a paragraph describing the images that you created and how the principle of color addition is evident in your final product. Be sure to explain why you are confident that this image reflects a 'true color' view of the object.
  • Submit your image and your paragraph to your instructor
    Instructor's Notes
    • Consider using activities 1 through 5 of the "Color the Universe" project as an enjoyable break from the usual preparations for the AP exam. Activities 1, 3, and 5 may be of particular interest to high school physics students.
    • A true color image is one where red, green, and blue color is assigned to images that capture only those wavelengths of light. The HST image files have the central wavelength of light capture by the picture specified in the file name. 
    • Most of the iconic HST images we see are not actually true color images. Scientists create their images to illustrate the many different features and subtleties of an object, but this may be misleading to the general public. The topic of whether or not this is deceptive could make for an interesting class discussion after the project is completed. 
    • After creating a true color image, students should be encouraged to try making color pictures using the other HST data sets and explore with various combinations of the astronomical images.

    Wednesday, February 15, 2012

    AP Physics
    Teaching waves with the iPad

    Learning Objectives
    Students will be able to demonstrate their knowledge of wave terminology, the principle of superposition, and resonance using iPad apps.

    Activity Type
    These activities could be used as an introduction to the associated wave topics, or they could even be used as a form of assessment. 

    Assignment Details
    • Each of the iPad apps below can be used by teachers or students to demonstrate physics principles related to wave motion, the principle of superposition, and resonance. For each app, a sample activity idea is provided. Each of the apps listed in this post are free educational apps available in the iTunes App Store.
    • String: This app consists of a simple string running the length of the iPad. Much like the "Wave on a string" simulation from PhET, you can adjust the properties of the string to make a variety of pulse, oscillating, standing, or traveling waves.
      • Make a wave activity: Students work as individuals or in groups to create types of waves specified by the instructor. They pause the screen to demonstrate to the instructor that they have successfully created the assigned wave type. For example, students could be asked to create: one fast and one slow traveling wave, a standing wave with two antinodes, or two pulse waves headed toward destructive interference. 
    • LU Wave Lab: This app acts as a virtual wave table with several different modes of operation. A simple touch on the screen can send a single 2D pulse wave in all directions or start a sinusoidal pulse oscillating.
      • Characterizing interference patterns: Students use the "sinusoidal wave source" mode of the app to experiment with how the separation between two pulsing sources influences the shape of the interference pattern. Student should try a variety of source arrangements to determine a general rule that describes the shape of the interference pattern based on the placement of the sources. After discussing as a class, formalize the rule by writing it on the board. Then ask students to predict what an interference pattern would look like with three oscillating sources. 
    • Fourier Touch: This app provides a wonderful illustration of the principle of superposition and Fourier synthesis. Any touch on the screen produces a sinusoidal waveform and an associated sound. The exact location of the touch on the screen influences the frequency and amplitude of the waveform. Multiple simultaneous touches produce multiple waveforms - each of their own frequency and amplitude. The sum of all of these waveforms is shown in the center of the screen.
      • Beat patterns demonstration: By selecting two waveforms that are very close in frequency, this app nicely demonstrates the beat pattern that emerges. The audio generated by the two waveforms will clearly illustrate the characteristic wah-wah of a beat. By making small changes to the frequencies of the two waveforms, you can convincingly show that the beat frequency is equal to the difference between the frequencies of the two waveforms.
    Instructor's Notes
    • Each of these activities could be modified for a one-to-one setting or a classroom with only a single iPad. If only one iPad is available, ask a student volunteer to come to the front of the room to use the app as a demonstration. 
    • In the LU Wave Lab, be sure that you modify the "mesh boundaries" setting to "MTC" to make sure that the waves don't bounce off of the walls of the simulation. 
    • For further analysis of sound waves include Fourier decomposition, you may consider using the free iPad apps: oScope Lite, Octave Lite, and Fourier Lite, which use the built-in microphone to analyze sounds by creating a frequency spectrum. 

    Tuesday, January 17, 2012

    AP Physics
    Challenge Circuits

    Learning Objectives
    Students will build several circuits using switches and principles of series and parallel circuitry.

    Activity Type
    This activity would best be used as an introduction to circuits and electricity. No previous experience in electricity or circuits is required for students to complete these challenges. This activity could also be used as a practicum component to a unit test on circuits and electricity. 

    Assignment Details
    • Teams of students will use a variety of simple circuit equipment (batteries, bulbs with holders, wires, alligator clips, and SPDT switches) to complete four circuit challenges. 
    • Circuit Challenges:
      1. String of Lights: Create a string of three lights that could be used for a Christmas Tree. If one of the three lights breaks (or is loosened from its socket) the other lights should still stay on.
      2. Lighting a Tunnel: Designing lights for a tunnel, you would like to be able to control two lights with one switch, which both turns on the light in front of you and turns off the light behind you. Create such a circuit. 
      3. Lighting a Stairwell: In this case we want to control one light with two switches - one at the top and one at the bottom of a stairwell. Wire a circuit with one bulb in which either switch can turn the bulb on or off at any time.
      4. Dimmer Switch: See if you can make a switch that would not only allow you to turn on and off a light, but also control how bright the light bulb gets. Try to create such a circuit. 
    • After a team completes one of the challenges, the team must demonstrate the function of the circuit to the instructor. Then, each student on the team must draw an accurate diagram that would allow them to rebuild the working circuit.

    Instructor's Notes
    • The circuit challenges are listed in order of difficulty with the easiest circuit first. It is acceptabe if some of the groups never reach the last two challenges, which are particularly tricky.
    • As you review the student circuits, be sure that they are not using a short in the circuit to make the light go out. Each of these circuits can be built without a short circuit. 
    • Proper understanding of SPDT (single pole double throw) switches is important for completing challenges #2 and #3. The "off" position of the switch must still make an electrical connection in order for students to create these circuits.
    • Students do not necessarily need to know about proper circuit diagrams before making their circuit drawings. In fact, it may be helpful for students to experience the difficulty of drawing a circuit before learning about circuit diagram conventions. 
    • Creating a dimmer switch (challenge #4) will require some way to change the current of the circuit. This could be accomplished by adding more than one bulb, or by adding a potentiometer (adjustable resistance device) to the circuit.