There's a famous analogy that explains the bending of light when it enters glass from air.

But doesn't that imply that two photons, represented by the adjacent wheels of the car, are connected by an axel? How could two distinct photons be connected like that, and what is the axel that connects them?

  • $\begingroup$ The wheels do not represent two photons. Honestly... analogies are not perfect. I would probably not even put this one among the good ones, either. $\endgroup$
    – CuriousOne
    Oct 18, 2014 at 7:53
  • $\begingroup$ @CuriousOne Then what do the wheels actually represent and what does the axel? Is axel something that actually breaks the analogy? $\endgroup$ Oct 18, 2014 at 7:55
  • $\begingroup$ One could think of the axle representing wavefronts, but in all honestly, I would not use this analogy to teach refraction. I don't think it helps. $\endgroup$
    – CuriousOne
    Oct 18, 2014 at 8:01
  • $\begingroup$ This is a poor analogy. "Famous"? In 40 years of doing physics I've never seen it. In addition to the complaints above, there's this: normally you stand behind a lawnmower and push it, controlling where you want it to go. To understand the analogy, you must understand in advance what it is trying to communicate. $\endgroup$
    – garyp
    Oct 18, 2014 at 13:20
  • 1
    $\begingroup$ A similar but better analogy can be found in this document, on the top of p. 463 (the third page of the pdf). I thought for sure there would be a youtube video of this demonstration, or at least a better picture of it, but it's all I could find in a quick search. $\endgroup$
    – garyp
    Oct 18, 2014 at 13:26


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