Reflection

2.8 Black boxes with mirrors

Test one's understanding of the behaviour of reflected light using black boxes. **

The solution of black boxes is a nice little puzzle which involves figuring out the position of one or more mirrors, knowing only the path of incident and reflected rays. The mirrors may be plane or curved. The solution of this problem requires:

• A solid knowledge of the behaviour of reflected light;
• A logical progression of steps, and especially...
• A bit of creative imagination.

Black boxes containing one plane mirror:

1. Extend the incident and reflected rays until they cross.
2. Determine the point of incidence on the mirror.
3. Draw the line that bisects the angle of deviation of the light (the normal).
4. Draw the mirror perpendicular to the normal.

Black boxes containing several plane mirrors
Black boxes containing one curved mirror