ABSTRACT
In this chapter, we shall take a quite general look at the nature of photons and electrons (and of their
interactions) in order to gain a familiarity with their overall properties, insofar as they bear upon our
subject. Clearly it is useful to acquire this ‘feel’ in general terms before getting immersed in some of the
finer detail which, whilst very necessary, does not allow the inter-relationships between the various
aspects to remain sharply visible. The intention is that the familiarity acquired by reading this chapter
will facilitate an understanding of the other chapters in the book.
