Reflection property of a parabola.

Author:
Imanpas
Move the three sliders a, b and c to change the shape of the parabola. Think of what each of them makes. Move the points A and B around. You can see how the rays going through those points (perpendicularly to the axis of the parabola) reflect on the parabola. All the rays go through the same point. Can you think of any technological application of this fact?