Two Prisms: Four Demos

Martin Sagendorfby: Martin Sagendorf

Most everyone knows that an equilateral prism will refract white light into its constituent colors: a spectrum ranging from red to violet.  But, if one uses two prisms, there’s much more to be discovered.

All that’s required:

–       a source of white light

–       a slit mounted on a large piece of cardboard

–       two equilateral prisms

–       two small pieces of card stock

–       a square of ground glass.


The light source and slit are arranged as shown.  A fairly narrow (1/4”) color spectrum will be displayed on the ground glass.  Note that the light beams are DIVERGENT.

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