An interactive applet and associated web page that demonstrate the optical properties of elliptical mirrors. Rays that pass through one focus of an ellipse always are reflected so they pass through the other focus. The ellipse can be resized by dragging, and light rays change to show that this is always true.

The web page also has links to other pages defining the various properties of an ellipse and to some ellipse constructions.

Applet can be enlarged to full screen size for use with a classroom projector. After use in the classroom, student can access it again from any web browser at home or in the library with no login required.

This resource is a component of the Math Open Reference Interactive Geometry textbook project at http://www.mathopenref.com.