  Using an analytical model, we compute the distribution of image separations
resulting from gravitational lensing of distant sources, for 7 COBE-normalized
CDM models with various combinations of Omega_0 and lambda_0. Our model assumes
that multiple imaging results from strong lensing by individual galaxies. We
model galaxies as nonsingular isothermal spheres, and take into account the
finite angular size of the sources. Our model neglects the contribution of the
background matter distribution, and assumes that lensing is entirely caused by
galaxies. To test the validity of this assumption, we performed a series of
ray-tracing experiments to study the effect of the background matter on the
distribution of image separations. The analytical model predicts that the
distributions of image separations are virtually indistinguishable for flat,
cosmological constant models with different values of Omega_0. For models with
no cosmological constant, the distributions of image separations do depend upon
Omega_0, but this dependence is weak. We conclude that while the number of
multiple-imaged sources can put strong constraints on the cosmological
parameters, the distribution of image separations does not constrain the
cosmological models in any significant way, and mostly provides constraints on
the structure of the galaxies responsible for lensing.
