SME Light Winter 2000 Laboratory 3

Week of Feb 8th, 2000

Activity 1: Symmetry and You Take a picture of your face and transfer it to your web page using the digital cameral and image processing equipment in the lab. Re-make the picture using first the right half of your face and its mirror image. Then re-make the picture using the left half and its mirror image. Save the picture in JPEG format--you will be transferring this to the web in Activity 3. The instructions for this part are by the computer with the digital camera.


  1. Humans are approximately "bilaterally symmetric." Sketch a few other common objects that are bilaterally symmetric.
  2. Could you rotate a human 180o (around a vertical axis) and have it appear unchanged? Why?
  3. Sketch a bilaterally symmetric object that has at least two mirror planes. Show where two of the mirror planes are.
  4. Even if your face and body appear perfectly symmetric, human beings are not really bilaterally symmetric. Where does the symmetry break down?
  5. Can you think of some reasons why bilateral symmetry might be advantageous for humans and other animals? Explain.

Bonus Activity: Ambigrams Play with the "ambigrams" at Ambigram your favorite word and put the image on your web page.

Bonus Question:

How many letter pairs did the designers need to make into ambigrams in order to make this site work?

Activity 2: Polarimetry For this activity, you will view the rotation of plane polarized light by Karo Syrup through a polarimeter. Karo Syrup is simply corn syrup and happens to rotate light fairly well. Go to the polarimeter station and follow the design instructions you will find there.


  1. Describe what you see when you place Karo syrup in your polarimeter and rotate the top polarizer (also called the analyzer). Use the light bench on the sink counter as your light source.
  2. By how many degrees does this column of Karo syrup rotate light? Assume that dark purple corresponds to minimum light transmitted.
  3. What do you see when you remove the bottom polarizer? You can use the already constructed polarimeter near the light source that does not have a bottom polarizer.
  4. What do you see when you place a colored filter between the bottom polarizing filter and the light source?
  5. Explain in your own words what the polarimeter is doing and how it works. Consider the roles of each of the polarizing filters and the Karo syrup in creating the effects observed in questions 1-3.

Activity 3: Setting up for the project.

  • Decide what project you are going to do.

    First, read through the project description handout with your group, and decide what project you are going to do. Agree on a tentative title for your project and write a one-paragraph description of it.

  • Make an index for your group's project folder.

    Do this using Netscape Page Composer (unless you're comfortable with html). The title of your project, your paragraph description, and a link to your activities.html file (described below) are all that needs to be on the index page for now. Save your index.html file to the desktop of one of the SME computers.

  • Transfer your index.html file to your group's project folder.
  • The project folders have already been set up on the SME web space. To transfer you file to your group's folder, fire up WS-FTP. Click the "ChgDir" button on your account's side (the right hand side) of the WS-FTP window. When the dialogue box comes up, type


    as the directory that you want to change to. When the right side of the dialogue box changes to the SME directory, you will see a bunch of files and some folders labeled with initials. Each member of your group has access to the folder that is labeled with the initials of the people in your group. For example, the folder labeled SSKGBOSW is the folder to which Sarah Schmidt, Kalee Gregory, Ben Olding, and Sharon West have access. Double click on your group's folder to enter it. Then transfer the index.html file that you made and any images over to that folder by clicking the arrows. Check to make sure that your file is there by opening up a browser and typing the URL

    (substituting your group's initials for SSKGBOSW).

  • Make an activities.html file and transfer it to your group's project folder.

    This file must display the following:

    1. All of your group's mirrored pictures from the first activity.
    2. Your favorite ambigrams from the Bonus activity.

    Check to make sure they're all there by typing in the URL on a browser: . Make sure the index.html has a link to the activities.html file. Check with your TA to make sure everything's in order.