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Re: A list of textbook misconceptions



One of my favorite misconceptions is one that is drawn by students on
seeing the standard picture of a ruler or pencil inclined in a glass
of water. The pencil looks bent at the surface of the water, and
students often take this to mean that the light bends just like that,
too. (Note that the pencil appears to bend away from the surface
normal where it enters the water.)

The lie can be given to this misconception by a concrete example. The
setup should not be too difficult to duplicate in the laboratory (or
the kitchen). Set it up. have the student sight down along the dry
part of the pencil. That should undo the misconception. It might even
encourage the student to think.

I think that this picture is worth far less than 1000 words; it has a
negative value. Given the tiny effort which must be expended to
instantiate refraction phenomena in the real world, do we really need
gratuitous and misleading photographs?

Leigh