warning: not the usual sign, the left side is reminiscent of a page on the physics of opticsarticle on the 4th. I have a dread reading the comments on the paper's internet site. It attracts many mean-spirited typists, some virulently noxious trolls. There was some comment on this and the 'Free Stamp', mostly unfavorable. Oldenburg has a first baseman's mitt inside the building, currently.
I like this installation. I looked at some of Kapoor's oeuvre. This is about the only one i like. It is a presentation of physics, whether that was his purpose or not. The 'C' is a double-sided mirror. The side that bulges forward in the center is a convex, or fish eye. It is used in store security. The mathematic lines have the focal points inside the mirror, so the image is not real (in size) but virtual. The closer the object, the larger it becomes, but always smaller than reality.
Here, both sides of the mirror are visible.