How big is the image of your face in a mirror? Bigger? Smaller? Equal? Or does it depend on the distance?

  • Stand in front of the mirror with your arm stretched out.

  • Close one eye and draw the outline of your face.

  • Open your eyes and look at your drawing - does it have the size of your face?

  • Walk away and get closer.

  • Does the dimension of the image of your face change?

How do you explain it?

mirrored modulator

The geometric explanation:

The image of our face forming behind the mirror is at the same distance from the mirror as we are. 

The silhouette we draw in the mirror is therefore right halfway between us and our image. Consequently as the drawing shows, their sizes are half that of the real ones and are independent of our position.