What you see isn't what you get

Sometimes science involves realizing that what you see isn't what you think you see and that what seems impossible has an explanation.

Materials:
Paper plate
scissors

Doing It
Plate pieces
1. Cut a paper plate in half.

2. Trim of the rim.

3. Cut the piece of the rim in half.

4. Hold the two new pieces together and trim them to make them exactly the same size.

5. Now put both pieces flat on a table, one piece above the other. Do the pieces look to be the same size?

6. Put the pieces into various positions. When do the pieces look the same size?

Strory behind the activity:
In plate pices, your eye-brain system compares the shorter upper arc of the one piece of plate rim to the longer bottom arc of the second piece. The bottom pice always looks shorter. The only way you can get around the optical illusion is to turn the top piece upside down. The shorther arcs then face each other and you see the pieces as the same lenght.