WOLFRAM|DEMONSTRATIONS PROJECT

A Parabolic Mirror

​
focal parameter p
10
number of rays n
3
2
y
= 20 x
Given a point F (the focus) and a line
d
(the directrix) that lie in a plane, the locus of points in that plane that are equidistant from F and
d
is a parabola.
One form of the equation of a parabola is
2
y
=2px
, where the focal parameter
p
is the distance from F to
d
.
This Demonstration illustrates the reflection property of parabolas. Imagine that the parabola is a mirror and that there is a light source at the focus. Then all the reflected rays are parallel to the axis of symmetry of the parabola.​