Disappearing Test Tube

Return to Refraction and Dispersion

Description:

Mineral oil and Pyrex have a very similar index of refraction. When the pyres culture tube is placed in the mineral oil slowly fills the test tube, and the tube "disappears." The demonstration usually used with this set-up is as follows: A test tube is placed in the mineral oil before the lecture. During the lecture, the lecturer smashes another test tube in an envelope and pours it into the oil and stirs it, then reaching in with a pair of tongs is able to pull a whole test tube out of the oil, telling the students it was put together by a special fluid designed by a collaboration between Chemists and Physicists in the material sciences.. Upon completing this trick, it is then shown that the test tube, when placed back in the mineral oil, disappears. It should also be shown that another test tube, placed in water, does not disappear because the test tube does not have the same index of refraction as water. We have made Pyrex bake ware and large Pyrex objects disappear n a fish tank,

ALSO Vegetable Oil and Vacuum Pump flushing oil also works. for this demonstration./

There is also a more expensive special oil used with glass slides microscopes that has the same index of refraction as glass.

Location:

• Oil and Culture Tubes: Shelf M-3
• Other Oils: Cabinet under Fume Hood