Physics Demo Number: 085
Approximate Run Time: 12min
Levitation With Mirror Cube (Floating Professor)
Demo Description
The demonstrator appears to balance on a few fingers (or totally levitate) with both feet elevated in the air. A mirror in the apparatus creates this optical illusion.
Scientific Principles
-
Reflection by a plane mirror makes a left foot (and leg) appear as a right foot (and leg) .
Equipment
-
4 plain PVC pipes
-
2 assemblies, each consisting of: 2 PVC pipes joined with 4 'three-pipe corner'- fittings to 2 steel pipes wrapped in yellow tape
-
1 Plastic Mirror with protective Paper Backing.
Equipment Location
-
[D-4-1] houses all the components.
1
2
3
Instructions
Photo 2 shows the first six components assembled to form a basic cube.
Note that one should be careful to ensure that the four yellow steel pipes are all assembled as shown so that they are all vertical.
This is necessary both for the symmetry required for the illusion and as a safety requirement for supporting any mantling type climbing maneuvers used in climbing in or out of the cube .
Maximum effectiveness of the illusion requires that both the cube and the Professor be on top of the lecture table, WHICH IS QUITE RISKY!!
For a safer demonstration, one should KEEP THE CUBE ON THE FLOOR.
Photo 1 gives the back view of the assembled apparatus (all 7 components).
Photo 3 shows the front view of the apparatus (all 7 components).
The mechanics of doing the illusion are to step into the cube with the mirror surface of the plastic plane toward the class. One steps into the cube astride the mirror. (Obviously female faculty need to be wearing something besides a skirt or dress.)
Suppose one has his left side facing the class, then his right foot and lower right leg will be be hidden from the class.
However the class will perceive the professor standing normally inside an open ( no mirror ) cube, with both legs fully visible.
One now supports all his body weight on the hidden right foot and proceeds to lift his left foot off the support surface.