The Effect of Geometrical Dimensions on the Image Position of the Thin Gravitational Lens

Abstract

When the gravitational lens is a galaxy or a galactic cluster, the effect of geometrical dimensions of the lens on the separation between the source and the image has been studied by using the thin lens approximation. A new form of the lens equation has been found. This equation shows the relationshipsbetween the basic parameters of the lens and helps in studying the mass distribution in the galaxy or the galactic cluster that behaves as a lens. This research clarifies that, at a very large distance between the observer and the lens, the
effect of distance from the observer to the lens on the image position decreases. Also, it shows that the effect of the impact parameter in the thin lens approximation is opposite to that which appears in the point mass approximation.

Keywords: Gravitational lens; Thin gravitational lens; Light bending; General relativity.