Mirror experiment – Shortest mirror
The following is a terrific way to learn that to see your entire body in a mirror you only need a mirror half the height of the person.
Ask a friend to stand in front of a full-length mirror. Stand ready with a non-permanent marker.
Ask your friend to tell you where to put horizontal lines on the mirror when they can see that they would line up with the top of their head and the bottom of their feet.
See below how the image would look.
A side view of this would be as follows:
Finally, measure both your friend's height and the distance between the mirror marks.
You will find that
The mirror `=1/2` your height.