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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
 Additive Color Mixing
 Line (discontinuous) Spectra
 Rainbow II
  video  - Sunset
 The Eye

Rainbow II


To show the dispersion of light through a prism.


Place the prism on top of the black paper slit used to create a thin column of light which enters the prism. The prism and black paper slit should rest on top of the overhead projector. The separation of the different colors of light due to the dependence of refraction on wavelength can be seen on the ceiling or classroom screen.


The equilateral prism is made up of flat plates of glass filled with ethyl cinnamate, a fluid with a refractive index of n = 1.52, higher than for water or glass, which have a lower n = 1.33. Actually, ethyl cinnamate has a higher dispersion (wavelength dependent refractive index) than other materials.

The prism has black "sun blocker" on top so that the white light from the slit does not project on the screen.