Figure A from George M. Hopkins, Experimental Science, Munn & Co., 1890. Photography courtesy of Michael Levin, Opti-Gone. (B, C); and by Donald Simanek (D, E)
C D E
a real image of your finger. With a little manipulation
of its position you can create the illusion of your real
finger just touching the real image of your finger
(Figure D). Since you have two eyes, you see this
illusion in three dimensions and can confirm the
CAUTION: Don’t let reflected sunlight fall location and orientation of the real image in space.
into your eyes. Never look directly at the sun Note that the image is reversed in all ways: up/
using any optical instrument, such as binoculars down, right/left, and top/bottom.
or a mirror. Children should always be supervised
when doing experiments with bright light.
The Phantom Reflects
Carefully place a small object at the very bottom of
the lower mirror. Now assemble the clamshell with
the upper mirror in place. Floating just above the
hole in the upper mirror, you’ll see a real image of
the object inside (Figure E). Note that the image is
rotated 180° about a vertical axis, with respect to
the object, but the image is still right side up.
One illuminating demonstration isn’t mentioned in
the user’s manual. Place the mirrors in the standard
arrangement, with a small object inside. Its image
appears just above the hole. Now shine a flashlight
onto the image, but aimed so that the light actually
Fig. A: The phantom bouquet, from George M. Hopkins’ Experimental Science, Munn & Co., 1890.
Fig. B: The Mirage optical illusion shows an image of a bolt and nut, as well as their reflection in the mirror below.
Fig. C: The Mirage shows another real image floating in space. Fig. D: Touching the real image (left) of your finger
(right). Fig. E: A real plastic frog (bottom) and its real image (top).
You can also demonstrate the convergence of
distant light to a focal point by using the sun as a
distant source. A small tissue of paper placed at
the focal point can be easily ignited.
Physicists call these images real images because
convergent light really passes through them, and then
diverges just as scattered light would diverge from a
real object. Real images are distinguished from virtual
images, such as those from a flat or convex mirror,
where the light rays don’t actually pass through the
space where the image appears to be located.
Touching the Real Image
Using only one mirror, place your finger at a distance
of about R from the mirror’s center. You should see