Mirror images in numbers

What if two mirrors work together?

15 minutes


  • Carefully review the general safety advice in the instruction book before starting the experiment.
  • Read the "Working with batteries" section of the safety guidelines carefully before proceeding. Always disconnect the setup after finishing the experiment.
  • Keep new and used coin cell batteries away from children.
  • Be careful working in dim lighting.
  • Disassemble the setup after the experiment.

Step-by-step instructions

Connect the LED to the battery and use it as a light source. Turn the battery over if the LED does not light up.


Construct your double-mirror setup.


Let the games begin! See how the number of reflections changes depending on the angle between the mirrors.


For the great finale, can you count the reflections when the mirrors are facing each other?


Add a fun twist to this experiment! Different mirrors reflect different amounts of light. Try switching out one of your mirrors for one that is somewhat transparent and see what happens!



  • Dispose of used batteries in accordance with local regulations.
  • Dispose of solid waste together with household garbage.

Scientific description

What does it really mean to reflect an object? For this experiment, you observed an LED  in front of a mirror. Some ambient light  passes through the transparent plastic casing of the LED , some is reflected from its non-transparent sections , and some light  is emitted by the LED  itself.

Each light beam is then reflected from the mirror at the same angle at which it hits the mirror’s surface. Altogether, this reflected light forms an undistorted image of the object, and it seems as if your LED  is duplicated behind the mirror.

Mirrors can also create all sorts of cool optical illusions! Two joint mirrors (  and  ) arranged in one plane work as one large mirror, creating just one mirror image of an object  in front of them. However, just start pivoting one of them around their joint axis, and the number of reflections changes. The sharper the angle between the two mirrors, the more images of the object!