* Pencil * Paper * Mirror
Stand in front of a mirror and write front to back on a piece of paper and observe how it looks in the mirror. Then write back to front and observe how it looks in the mirror.
This change in direction in the mirror is because of the reflection of light on reflecting surfaces where light is reflected on the other side.
When you write front to back, the mirror shows you writing from back to front, it shows you writing from front to back when you write from back to front.