In astronomy, the parabola features in both the construction of telescopes and in the motion of comets around the Sun. A parabola is one of the four conic sections - a plane intersecting a cone parallel to one edge traces out a parabola. A parabola has the functional form: *y*=*A x*^{2}where *A*is the*constant of proportionality*.**Parabolas in Telescope Design**The parabola is the exact shape required to focus a plane wave to a single point. Hence parabolic dishes coherently (i.e. in phase) add electromagnetic radiation at a point and are central to many telescope designs in both the optical and radio.

For a parabola of equation*y*=*A x*^{2}, the point of focus lies at (*x*= 0,*y*=*A*/4).**Parabolas in Nature**Curiously a comet falling from a great distance towards the Sun will trace out a parabolic orbit with the Sun at the focus of the parabola. This is just a consequence of Newton's laws of motion and gravitation. Similarly a projectile on Earth follows a parabolic arc as it falls under gravity.