E1-21: GRAVITATIONAL LENS OPTICAL MODEL

ID Code: E1-21
Purpose: Demonstrate optical characteristics of a gravitational lens.
Description: The lens shown in the photograph at the left above is a plano-convex lens whose focal characteristics model that of a gravitational lens. The shape of the lens, described in one of the reference articles in the reference list linked below, is seen in the photograph at the right.

The experimental setup is shown in the photograph at the right. The distant "star" is formed by a hole in a piece of black paper in front of a light bulb. The star can be moved by sliding it left-to-right along the optical rail behind the gravitational lens, in the same plane as the observer (video or other camera). Adjusting the height of the camera will put the observer slightly out of the plane of the motion of the star and axis of the gravitational lens.

This device was designed and produced by physicist Sid Liebes, an expert on gravitation and relativity, and author of several of the reference works, including both the design and application of the lens

Availability: Available

An animated simulation of gravitation lensing by a black hole can be found at commons.wikimedia.org/wiki/File:Black_hole_lensing_web.gif .

And an amusing related image from Hubble: www.spacetelescope.org/images/potw1506a/

A new article in The Physics Teacher on using a similar demonstration in the classroom: dx.doi.org/10.1119/1.4917429