Mirrors are counter-intuitive

Most people don’t understand how mirrors work.  For example, when presented with the following scenario, most people get it wrong.

Imagine you’re at the entrance to a narrow corridor and further down, several feet away, hanging on the right-hand wall, there are three rectangular mirrors (30cm x 45cm) at head height. At what point, as you proceed down the corridor, do you think you’ll be able to see your face in the mirrors?

In another demonstration of the fallibility of our intuitions when it comes to mirrors:

If I asked you to draw a full-size outline of your head on a flip chart, and then to draw the outline of your head as it appears in the mirror, would you draw the two outlines the same size? You shouldn’t do because the mirror image of your head (as it appears to you) is exactly half its true size, irrespective of how far you are from the mirror, a fact that few people realise.

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