School of Physics Lecture Demonstration Manual

Aa-2 Gravitational lensing

Published: Tuesday 05 June 2007 - Updated: Thursday 31 March 2011


To demonstrate gravitational lensing via a simple optical analogue.



Click on pictures to enlarge.

Grav Lens Setup Pic

Grav Lens pic 1

Grav Lens pic 2


A simple model of a gravitational lens has been constructed by using the base of an ordinary glass. If the lens is placed over a small dot (representing a galaxy) drawn on an overhead transparency the lens will spread the image into a circular ring. The lens mimics the gravitational effect of a mass positioned between the earth and a distant galaxy. The bending of light near a gravitational mass simulates an optical lens. By placing the lens slightly off axis instead of a full ring two arcs are produced as shown in the photograph displayed.

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