Parabolic Reflection
Reflection Property of a Parabola
Any ray parallel to the axis of symmetry of a parabola will reflect to the focus regardless of its position. The slider changes the position of the source while keeping the ray parallel to the axis of symmetry. The sliders and offers a way to move the source such that the ray direction is not parallel to the axis of symmetry anymore.
Play around with these sliders and observe the behavior of the reflected ray.