  The propagation of light through a Universe of (a) isothermal mass spheres
amidst (b) a homogeneous matter component, is considered. We demonstrate by an
analytical proof that as long as a small light bundle passes {\it through}
sufficient number of (a) at various impact parameters - a criterion of great
importance - its average convergence will exactly compensate the divergence
within (b). The net effect on the light is statistically the same as if all the
matter in (a) is `fully homogenized'. When applying the above ideas towards
understanding the angular size of the primary acoustic peaks of the microwave
background, however, caution is needed. The reason is that most (by mass) of
(a) are in galaxies - their full mass profiles are not sampled by passing light
- at least the inner 20 kpc regions of these systems are missed by the majority
of rays, while the rest of the rays would map back to unresolvable but
magnified, randomly located spots to compensate for the loss in angular size.
Therefore, a scanning pair of WMAP beams finds most frequently that the largest
temperature difference occurs when each beam is placed at diametrically
opposite points of the Dyer-Roeder collapsed sections. This is the {\it mode}
magnification, which corresponds to the acoustic {\it peaks}, and is less than
the mean (or the homogeneous pre-clumping angular size). Since space was seen
to be Euclidean without taking the said adjustment into account, the true
density of the Universe should be supercritical. Our analysis gives $\Omega_m
=$ 0.278 $\pm$ 0.040 and $\Omega_{\Lambda} =$ 0.782 $\pm$ 0.040.
