Editing Paraboloid (section)

====Parabolic reflector====
{{main|Parabolic reflector|parabolic antenna}}
On the axis of a circular paraboloid, there is a point called the [[Focus (optics)|''focus'']] (or ''focal point''), such that, if the paraboloid is a mirror, light (or other waves) from a point source at the focus is reflected into a parallel beam, parallel to the axis of the paraboloid. This also works the other way around: a parallel beam of light that is parallel to the axis of the paraboloid is concentrated at the focal point. For a proof, see {{slink|Parabola|Proof of the reflective property}}.

Therefore, the shape of a circular paraboloid is widely used in [[astronomy]] for parabolic reflectors and parabolic antennas.

The surface of a rotating liquid is also a circular paraboloid. This is used in [[liquid-mirror telescope]]s and in making solid telescope mirrors (see [[rotating furnace]]).
<gallery widths="200px" heights="180px">
Parabola with focus and arbitrary line.svg|Parallel rays coming into a circular paraboloidal mirror are reflected to the focal point, {{math|F}}, or ''vice versa''
Erdfunkstelle Raisting 2a.jpg|Parabolic reflector
Centrifugal 0.PNG|Rotating water in a glass
</gallery>