I hope you will continue to be interested in the properties of light --
electromagnetic energy is used for a great variety of purposes. Only a
small number of these purposes are meant to deceive observers. As
physicists and truth-seekers and skeptics, we don't specialize in
deception, and in fact try to dispel it whenever it arises. Those who
do specialize, "magicians" or more appropriatley termed "illusionists",
hide their secrets very carefully so that their shows remain
entertaining to people who do not know their secrets. I can only offer
a few small tips on the subject (not being an expert):
1) Make it entertaining and quick and do not show the setup more
than once to any particular person. The reson for this is that mirrors
are often easy to detect because what people see in mirrors looks
reversed, and often appears to be farther away than the object the
mirror is attempting to conceal. Two mirrors can fix the reversing
problem, but then the combined image degradation may spoil the illusion
(i.e., if there is dirt on the mirrors or they aren't perfectly flat or
if the edges aren't concealed well).
2) Reflect a bland, featureless background -- that way people will
have a harder time noticing that it is a reflection they are looking at
and not the real thing. The background may not be the same as the
background the audience thinks it is looking at. For example, placing
an object in a box with interior walls painted a bland, light color,
and then inserting a mirror so that a viewer sees a reflection of a
side wall instead of the back wall makes for a passable trick. But the
viewer has to be convinced that he is looking at the back wall, which
means he cannot see the edges of the mirror or any other defects. It
also confines the whole demostration to the box. And you have to slide
in the mirror when no one's seeing you do it (and that's the biggest
trick of all). One thing you can do is have a box with one side missing
for viewing, a mirror arranged diagonally so that the side looks like
the back, and then conceal a heavy weight in the part of the box that
is invisible. Then it looks like an empty box, but a person picking it
up will be amused to find how much it weighs.
3) The mirror only needs to be as big as the object it conceals.
You can make these as small as you like (but not smaller than the
wavelength of the light -- see our answer on diffraction.)
The whole purpose of illusion is to make an observer think he's
looking at something that really is different, and mirrors can help
this by bouncing light in different directions. Use your own creativity
to find uses for them!
Tom
(published on 10/22/2007)