Photocopy A Mirror

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Photocopy A Mirror - 2015/07/29

Recently on Twitter I asked the question:

  • What do you get when you
    photocopy a mirror?

There are actually (at least) three inter-related questions:

  • What do you get?
  • How does the photocopier give you that?
  • Why is that the right thing for it to do?

Several people engaged with the question. One said "Just try it!" and that's perfectly reasonable, but it only answers the first of this set of three. Someone else pointed at an answer on Quora that correctly explained how the result is obtained, even though it claims:

  • "To understand why we got the result we did,
    we first need to look at how a scanner works."

No, that's not the why, that's the how. It explains what happens, but it gives no clue as to why the photocopier is designed to work like that.

So we are left wondering why. Why do we get the result we do when we photocopy a mirror? Can you deduce, purely from what a photocopier does, what the result should be when you photocopier a mirror?

To quote Julius Sumner Miller:

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You should follow me on twitter @ColinTheMathmo


I've decided no longer to include comments directly via the Disqus (or any other) system. Instead, I'd be more than delighted to get emails from people who wish to make comments or engage in discussion. Comments will then be integrated into the page as and when they are appropriate.

If the number of emails/comments gets too large to handle then I might return to a semi-automated system. That's looking increasingly unlikely.



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