  In this manuscript, we present an alternative method for calculating null
geodesics in General Static Isotropic Metrics in General Relativity and
Extended Theories of Gravity. By applying a conformal transformation, we are
able to consider an analogue gravity model, where curvature is encoded in the
dielectric and magnetic properties of a medium. In other words, we pass from
curved to flat space-times, where instead of the Einstein field equations, the
Maxwell equations are solved. Within this geometrical background, the photon
geodesics are calculated. Then, given different black hole and wormhole
metrics, we apply this method obtaining an excellent agreement with respect to
the exact solutions in the original gravity framework by committing angular
deviations below $3^\circ$. Finally, we provide the image of a Schwarzschild
black hole surrounded by a thin accretion disk, and the apparent image of a
Morris & Thorne-like wormhole within an angular discrepancy below $4^\circ$.
