I read this book in high-school and learned about as much as I did in 4 undergrad physics courses about quantum mechanics.
There's no mathematics in this book, so it doesn't teach you how to calculate anything (for this, a physics degree helps), but the principles are presented very nicely.
The short answer is, they don't. They emit the photon in a random direction.
Fine, you say, but what about refraction and reflection, there the photons are emitted in another direction. What makes the atom "decide" what direction to emit a photon after it's absorbed?
They don't decide anything, they still just emit in a random direction. The mind fuck is that on the whole, statistically, almost all photons except for those travelling in the direction of refraction/reflection destructively interfere!
Out of all his writings, this is the one that has always stuck with me.
Feynman long held that one does not understand something if one cannot explain it to someone who is not deeply steeped in the subject already. I regard this lecture as probably the culmination of that philosophy for Feynman. Anybody with a deep mathematical background will be stunned on reading this book to realize that, oh, he was actually just talking about complex numbers and the path integral formulation all along.
Taken from one of those reviews, I don't need to say much more than this: "He does close to the impossible by explaining the rudimentary ideas of Quantum Electro Dynamics (QED) in a manner that is reasonably accessible to those with some physics background"
It's very complicated stuff but not "very, very complicated" stuff, you can read Feynman's QED book (http://www.amazon.com/QED-Strange-Theory-Light-Matter/dp/069..., <$9 used with shipping) and obtain a pretty good working knowledge of things.
If you don't really understand what this article is talking about, Feynman can help you.
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