Now, it is time to make the "lens".



You will need to make two arches with long sides measuring 30.0cm which will allow them to be attached to your trapezoidal prism projector.



*The images for this step should clearly illustrate the process but I will also describe them:

- Measure out 30cm straight line on your foamcore or cardboard and cut a piece of string to the same length (represented in the images as the line which connects A to B).

-Find the center-point of the 30cm line on your foamcore/cardboard and draw a 15cm long line at a 90-degree angle from that center point (represented by point C in the images).

-Now find the center of your string and while holding its center-point to point C, stretch each end of the string so that it touches the line connecting A and B while being as taught as possible. Mark the two points that the ends of your string touches. We will call these new points, 1 and 2.

- Use a tack, pin or tape to secure the string to points one and two.

-Now with the string secured to points 1 and 2, you should be able to slide your pencil along the inside of the rope between points A, B and C in order to draw your desired arch. By keeping the string taught, you can draw a line on the board to mark your arch and the string will self adjust to keep the appropriate distance from the center point.

- Cut out your arch and then use it as a stencil to trace another exactly like it, then cut out the second arch as well.

- Use spray adhesive to glue aluminium foil to one side of each of your arches.