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EXPERIMENT
Optical
Illusions
Magicians
often use optical illusions to entertain their audience and
this demonstrates another way our sense of sight can be fooled.
We can make our own illusions or we can see them in nature.
Clouds that look like familiar objects and the man in the
moon are examples of natural illusions. Clever artists, like
M. C. Escher, have made great drawings based on optical illusions.
A lot of people have reported seeing faces in potato chips
or on the windows of buildings. Usually the objects they see
are examples of optical illusions or simply coincidence and
active imaginations.
You
can make your own optical illusions:
The
Moebius Strip:
You'll
need:
- Make a circle
out of one strip of paper and tie the ends together. Cut
it in half around the middle.
- Now take
another strip of paper but this time put a half-twist
in it before you tape the two ends together. Cut it in
half around the middle again. Any difference?
- Find out
what happened by doing the experiment over again. Make
two more circles of paper, one with a half-twist and one
without.
- To test them
take the plain circle and with your one marker trace a
line along the outside until you return to the beginning.
With the other colored marker draw a similar line on the
inside of the circle.
- Now do the
same with the twisted circle!
The
circle with the half-twist is the Moebius Strip. When you
cut your two-sided, two-edged strip in half, you get two pieces,
with a total of four edges and four sides. When you cut the
Moebius Strip in half it's still in one piece, but how many
edges and sides to you have?
The
Ghostly Tree:
Take
a flashlight into a dark room. Close one eye and cover it
with your hand. Shine a flashlight at your open eye while
you look at a blank wall. After a while you should see the
image of a leafless tree in the dark area of the wall. This
image is made by the blood vessels on the back of your eye!
The
Bent Pencil:
Hold
a pencil in a glass cup of water so that only half of the
pencil is in the water. If you look at it from the side, the
pencil will appear bent. The light rays are bending when they
move from air to water because the mediums the light is traveling
through are different. This is what makes the illusion. This
is also the reason why people can appear to have shorter legs
in a swimming pool.
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