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Crookes Tube

The object is an enclosed glass tube with two smaller tubes extending horizontally off the main body. One end of this tube is broad, concluding in a flat end. In the trunk of the main tube, at one end, there is a small circular metal plate. This is connected to a metal cap which extends outside the glass and ends in a metal loop. The small tube closest to this end of the main tube is long and empty, with a broader section about half way along its length, and concluding in a point. Above the broad section, it has a secondary tube coming off it, with a thick piece of metal wire that extends along its length and is connected to an metal cap on the outside of the tube, with a loop identical to that attached to the main tube. The second tube, closer to the broad end of the main tube, consists of a thin metal wire that extends along its length from the closed end of the tube, culminating in a Maltese cross that extends into the main tube of the apparatus. The cross is on a hinge allowing it to stand up or lay mostly flat.

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Primary Materials: Glass, Metal: Iron Alloy

Markings: Old Cataloguing number: “PHY 70”

Dimensions (cm): Length = 21, Width = 7.5, Height = 16.5


The Crookes tube is used to demonstrate the fluorescent properties of high-velocity electrons when they interact with glass. The cross casts a shadow to indicate that the electrons are flowing towards it rather than away from it. The cross can be laid flat. When this is done, the unexposed shadow on the glass glows more brightly than the surrounding area, demonstrating that over time the glass glows less.


Excellent. The tube shows no sign of damage or wear..

Associated Instruments:


Date of Manufacture: Early 20th Century


Department of Physics, University of Toronto

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