The Disappearing Beaker

This is what the famous "disappearing beaker" is supposed to look like. The index of refraction of the inner glass must be a very close match to that of the oil for the trick to work. Pyrex and canola oil work well. Some students claim that it also works with a shot glass and beer, but that seems unlikely (no, impossible) - why?

Variations include smashing a test tube and pouring the pieces into a beaker of oil in which a whole test tube is hidden. Appropriate magic words and the whole tube is pulled from the oil.

Some students have noticed that the beaker is faintly visible upon close inspection, sometimes with a blue tint. It may be that the index matching is not equal across wavelengths.


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