Reflection in Variable-Angle Mirrors
Two mirrors set at an angle produce multiple images, and the number depends on that angle in a surprisingly simple way. This simulation lets you close and open the pair while counting the images that appear.
How to use this simulation
- Change the angle between the two mirrors
- Move the object between the mirrors
- Trace individual ray paths to a chosen image
What to look for
- Two mirrors at 90° give three images; at 60° they give five
- Images lie on a circle centred on the line where the mirrors meet
- Closing the angle further multiplies the images rapidly
The physics behind it
Each mirror reflects both the object and the images formed by the other mirror, producing a chain of reflections. For two mirrors at angle θ the number of images is 360/θ − 1, provided that ratio is a whole number. As the angle closes, the images multiply — the kaleidoscope effect — and at 0° the images become endless.