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Al Tobias (wat4y) - Office: Gibson S123 & Physics 218, (434) 924-0538

Physics Demo Manual

Demonstrations are cataloged according to PIRA Bibliography


Due to Physics Building renovations, the lead time to set up demo requests has increased due to the need to transport equipment across campus. Please be kind and let me know well ahead of time what you need.

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 Geometrical Optics
 The Eye
 The Eye Model I
 The Eye Model II
 Image Retention

Image Retention


To illustrate the ability of the eye to retain an image longer than it is physically present.


Focus the projector at a point away from the wall. Stand to the side of the light path and wave the meter stick up and down in the path of the light. If the frequency is not too low the class can see the entire image of the slide, even though the "screen" is only a couple of centimeters wide. At lower frequencies less of the slide can be seen. This shows that the eye retains an image for a short while after receiving it.


An alternative set up where projector is shining through the blades of a speed controlled fan is available.


  • Slide Projector
  • Colorful Picture Slide
  • Meter Stick Wrapped w/ White Paper