Pinhole Viewer

• Make two tubes out of construction paper, one slightly larger than the other, so that the larger slides over the smaller.
  
• Use a rubber band to secure aluminum foil over the end of the larger one. Prick a pinhole in the center of the foil.
  
• Tape wax paper over one end of the smaller tube. Slide the wax paper end into the larger tube.
  
• Look through the open ends.

     

  • What does the image look like?
    
  • Is it inverted or upright? Why? (There is no lens.)
    
  • What does this tell you about how light travels - in a straight line or not?
    
  • Can you see near and far objects? How can both be "in focus"?
    
  • How is a pinhole viewer similar to a person who squints to see better?

  2-Dimensional Mirrors

  • Cut a rectagular piece of plastic mirror, about 1 inch by 8 inches.
    
  • Cut a rectangular piece (about 10 inches by 4 inches) of one-inch wood.
    
  • Cut a rectangle out of one side. It should be smaller than the mirror.
    
  • Bend the mirror as you force it into the cut-out piece.
    
  • Bend it the opposite way to make a different curved mirror.

     

  Cheap Light Box

  • Obtain a round ice cream box from an ice cream store. (You want a round box, so the the edge is all equi-distant from the light in the center. If you use a rectangular box, the light rays won't be parallel.)
    
  • Cut slits or make slits by taping popsicle sticks over an opening.
    
  • Cut a hole in the top for the cord of a "showcase" light, which is a long, narror, clear light bulb. You can find them in hardware stores.
    
  • Use lenses, mirrors (see 2-dimensional mirrors above), and colored filters.
    
  • Be sure that the light is not close enough to the table to scorch or burn it. (I speak from experience!)

     

  February Optics

  PTRA workshop schedule