Reflecting inside a Spherical Mirror and a Catacaustic

This Demonstration shows an image formed inside a spherical mirror of radius and center on the optical axis . Let the point be off and let be the orthogonal projection of onto . After reflection, the reflection of the ray parallel to from meets the ray at the point . The notion of image of a point is not uniquely defined because the reflections of three rays from a given point do not meet in a single point. The image of the directed segment is a vertical segment with endpoint as . If you increase the height of , moves to the right.