Re: "one-way" mirrors?

[Kathy Daniel <danielka@BELLSOUTH.NET>]

.
> Partially-silvered mirrors in small size can be bought from Edmund
> Scientific for reasonable cost, and are good to have for experiments.
I have made some adequate (we call them half-silvered) mirrors by using
regular glass plates like in a picture frame and covering one side with
some car window tinting plastic.  Its hard to keep the bubbles out when
putting the plastic tinting on, but it works well especially to show
that the object distance and the image distance with a plane mirror are
equal and that the eyes are focusing BEHIND the mirror to see the image
and not on the surface of the mirror.

Students put a light source on one side and then try to place an
identical light source at the position where they see the image. You see
a great reflection of the source when no other light is behind the
vertical half silvered mirror, and you see both the reflection and the
2nd light source on top of each other when they are lined up properly.
This has been one of the best lab activities I have used to impress upon
the students that the image is not on the surface of the mirror.

Kathy Daniel
Oakland High School
Murfreesboro, TN  37130