bbaskii:
I have been reading a book titled QED ,the strange theory of light and matter, the book is written by an highly intelligent man Richard P. Feynman. The book is written in laymen terms. The book, 152 pages, can be read in about 8 hrs. The topics of the book deals with the question you have asked. I have not read the fourth lecture within the book and would sepculate that it would be fould there. Hope this is of help and you have 8 hrs. to read this enlighting material.
xray;