Obtain/cast a clear block of glass, preferably of high refractive index, preferably already molded into a suitable shape. Polish/grind//cut to shape if not already suitably shaped. Grind/polish surfaces to optical quality.
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Ever tried it, for real ?
(I think he was being sarcastic)
Not entirely sarcastic -- just pointing out that doing it right is a nontrivial project, and it's cheaper and easier to buy unless you are have special needs or are particularly attached to doing it yourself.Actually, you can make a _small_ prism by grinding/polishing a suitable bevel into the edge of a sheet of glass. My bathroom mirror has some decorative triangular grooves ground into it, and when the light hits them right they do disperse colors.Acrylic/plexy is, of course, easier to work than glass. I don't think you can fire-polish plastic, though.
I remember seeing a local man who ground down tv tubes into prisms. Been looking for anything like it so I can get more details.
A real one, or a toy ? A toy one I'd make in plexiglass.
Or as three sheets of glass glued together, stoppered at one end, and filled with water. (Or... Hm. What's the refractive index of lamp oil? Lower or higher?)
You can buy clear resins as well - "fake water" etc.
Good point. I remember casting some biological specimens in plastic, back when I was a kid. (The resin used for the purpose actually penetrated the tissues and made internal details visible; impressive.) Something like that which is very transparent, polished appropriately, seems entirely reasonable -- assuming that it is a dispersive medium (which it probably is).
That's another classic method, for toys.
I have hand ground and polished small prisms, it's very hard to get the angles spot on!!!
In acrylic. A triangular container and water works.