>I appreciate all the discussion and glad everyone agrees as to the
>answer.  Getting to the issue of intuitive explanations, let me
>display my ignorance once again explain why I found this so confusing
>and see if we can come to an intuitive explanation that agrees with
>the "real" one.

How about this;

The "wave crests" really just represent high probabilities of finding
a photon: troughs represent low probabilities.

Adding waves that approach the focus from higher angles (higher NA)
makes the final spot smaller because the crests and troughs of these
high NA "rays" have the correct phase to cancel out (or at least
reduce) the "photon probability" present around the edges of the
larger spot produced by the addition of the crests and troughs of the
lower NA rays.

The high NA rays represent an additional constraint about where
photons can exist.

Jim P.
--
               ****************************************
Prof. James B. Pawley,    (on Sabbatical)       Ph.  61-2-9351-7548/2351
Room LG 10, Madsen Building, F-09,              FAX  61-2-9351-7682
University of Sydney, NSW, 2006 Australia       [log in to unmask]
"A scientist is not one who can answer questions but one who can
question answers."      Theodore Schick Jr., Skeptical Enquirer,
21-2:39