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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
 Speed of Light
 1/r2 Demonstrator
  video  - Ray Optics Kit
 Confocal Mirrors
 Concave Mirror
  video  - Light The Match
 Disappearing Beaker
 String Model of Refraction
 Total Internal Reflection
 Steal the Light
 Light Pipe and Fiber Optics
 Water Light Pipe
 Thin Lenses with Objects
 The Eye

Confocal Mirrors


To show another 'real' image.


The two concave parabolic mirrors with the correct focal length and spacing project the real image of the object, making it appear to levitate on the opening of the upper mirror. The ray drawing below shows how the image is produced by the double reflection from two concave mirrors.

Place mirrors on table and have students try and grab the bolt. The image is real and looks so but cannot be touched. The image can be viewed within a limited angle, so it is most effective for individual observation. It is possible to setup a video camera for large classes.

Care must be taken to keep fingers out of the hole as the mirrors are very thin and extremely difficult to clean.


  • Confocal mirrors and large bolt