The Focus of a Parabola
A ray falling onto a mirror will have a reflection such that:
the incident angle = the angle of reflection
Exercise
Show that a ray falling onto a parabola perpendicular to the directrix will be reflected to the focus point. In other words, show that α=β.
by Malin Christersson under a Creative Commons Attribution-Noncommercial-Share Alike 2.5 Sweden License
