Comment author:David_D
19 April 2008 03:25:06PM
5 points
[-]

If that still doesn't work, read an actual book on quantum mechanics. Feynman's QED is a great place to start..

Since I was pretty much lost after the first few posts in this series, this is exactly what I am doing. I've gone through the first 2 chapters, and what has surprised me is that at least one part of it (explaining why light "bends" when it goes through a material with a different refractive index) has been MORE intuitive to me than the "classical" explanation. The explanation (or shall I say, analogy) I have always heard is that light is like a bunch of soldiers that "want" to stay in line, so when they hit a patch of mud (i.e. when they have to move slower) they change direction. Another explanation I have been given (which is a bit closer to the QED one) is that light "wants" to get from point A to point B as fast as possible, so it "chooses" the path through the glass (or whatever) that will accomplish this.

The QED explanation (i.e. all of the fastest paths tend to have similar phases so they do not cancel each other out like the slower ones do) was much more satisfying.

FWIW, learning about amplitudes in terms of complex numbers before I started reading the book really helped me grok the arrows that Feynman uses. Otherwise, it would probably take my brain a few steps to keep the "amplitude arrows" and the "possible path of the photon arrows" separate.

Anyway, if anybody reading these posts are as lost as me, I would strongly recommend the QED book.

## Comments (68)

OldIf that still doesn't work, read an actual book on quantum mechanics. Feynman's QED is a great place to start..Since I was pretty much lost after the first few posts in this series, this is exactly what I am doing. I've gone through the first 2 chapters, and what has surprised me is that at least one part of it (explaining why light "bends" when it goes through a material with a different refractive index) has been MORE intuitive to me than the "classical" explanation. The explanation (or shall I say, analogy) I have always heard is that light is like a bunch of soldiers that "want" to stay in line, so when they hit a patch of mud (i.e. when they have to move slower) they change direction. Another explanation I have been given (which is a bit closer to the QED one) is that light "wants" to get from point A to point B as fast as possible, so it "chooses" the path through the glass (or whatever) that will accomplish this.

The QED explanation (i.e. all of the fastest paths tend to have similar phases so they do not cancel each other out like the slower ones do) was much more satisfying.

FWIW, learning about amplitudes in terms of complex numbers before I started reading the book really helped me grok the arrows that Feynman uses. Otherwise, it would probably take my brain a few steps to keep the "amplitude arrows" and the "possible path of the photon arrows" separate.

Anyway, if anybody reading these posts are as lost as me, I would strongly recommend the QED book.