Gravitational Lensing Lab
The purpose of this lab was to try to emulate the effect of gravitational lensing using a flashlight and a 1.5L wine bottle, flipped upside down and with water in the bottom. The theory behind this is that a lens can be made that focuses light just like a black hole; such a lens would look much like the cavity in the bottom of a large wine bottle. So we simply took such a bottle, filled the inverted bottom with water to form a lens of the appropriate shape, and shined a flashlight through the bottle, to simulate a light source, such as a star, that would be bent by such a lens.
Gravitational lensing occurs when a black hole, or another object with a very great mass, bends light as the light travels around it. Light is bent so that it focuses not at a point, but along a line, much like what happens when one uses an ordinary spherical lens to focus light.
A telescope filters out portions of the light that focus at the wrong distance for it; it acts much like a pinhole camera, because only light that comes to a focus at exactly the right distance can make it into the telescope's apereture.
The result of this blocking-out effect causes a ring of light to appear through the telescope. Our goal through this lab is to investigate an apparatus that simulates the lensing effects of a very massive object, in an attempt to simulate and study these rings.
We took many pictures during this lab, and I have uploaded most of them to this site. It would be unfeasible to fit each of the many pictures into a concise lab; those that I chose not to include in the actual lab can be found here.
The final configuration
The manilla folder wrapped around the top of the wine bottle was to support the paper plate. The plate had a pinhole in its center; that pinhole was used to simulate the lens of a telescope, viewing the gravitational lens from a distance. By adjusting the distance of the pinhole from the gravitational lens, it is possible to vary the image produced through the lensing system.
This is a basic diagram of how the pinhole works:
The light is reflected around the lens in many different ways, but only one of the given reflections, corresponding to one ring of light from the light source, makes it through the pinhole. As a result, a gravitational lens produces a very bizarre ring-like image, called an Einstein Ring.
After getting the apparatus set up, we created, and took pictures of, Einstein ring images. We attempted to get clean-looking, precise images.
The next part of the lab was to compare the pictures that we took to pictures of real Einstein rings: