2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/171618Using the Eikonal approximation we study the effect of the smoothness parameter in the Dyer-Roeder equation. We calculate the optical depth for dark halos with NFW profile, for the abundance the Press-Schechter formalism is used. We focus our analysis on the cross section for multiple images (three). Different cosmologies are compared.Latex, 4 pages, 3 figures. To appear in the Proceedings of 30th Spanish Relativity Meeting (ERE 2007): Relativistic Astrophysics and Cosmology, Puerto de la Cruz, Tenerife, Spain, Sep 10-14 2007Astrophysicstext