Why do photons “prefer” to take the path (to the destination) which takes the least amount of time?

Question: Why do photons "prefer" to take the path (to the destination) which takes the least amount of time?
- Keywords:
  photon,
  photons
Asked by strangeness to Arttu, Ceri, James_M, Monica, Philip on 20 Jun 2011.
- Arttu Rajantie answered on 20 Jun 2011:
  
  We don’t usually have good answers to these “why” questions, but this is an example of a more general principle in quantum mechanics. In quantum mechanics, one could say that particles take simultaneously all possible paths to their destination rather than just a single one. Each of these paths has a quantity called “action”. For the photon, the action is just the time it takes to follow the path. Now, in general the final outcome is a kind of an average over these paths calculated using the action, but in simple cases only the path with the lowest action matters, and for the photon that is the path with the least amount of time.

strangeness commented on 23 Jun 2011:

So is this effect the real cause of phenomena such as reflection and refraction?

Log in to Reply

Question: Why do photons "prefer" to take the path (to the destination) which takes the least amount of time?