mirror image
This is one of my favorite demos. I like it because anyone can do it at home and people usually find the results surprising. Here is the situation:
How much of yourself could you see in a small mirror? What if you move farther away from the mirror, can you see more of yourself? If you want to do the demo yourself, now would be a good time. All you need is a small mirror (I used a platter from a 10 GB hard drive - they make awesome mirrors). It will help out a lot if you can mount the mirror on a surface that is very near to vertical.
Here is my version of this demo (in case you can't…