In mathematics, a paraboloid is a quadric, a type of surface in three dimensions, described by the equation:
- (elliptic paraboloid),
- (hyperbolic paraboloid).
With a=b an elliptic paraboloid is a paraboloid of revolution
: a surface obtained by revolving a parabola
around its axis. It the shape used by the parabolic reflectors used in mirrors, antenna
dishes, and the like.
A point light source at the focal point produces a parallel light beam. This also works the other way around: a parallel beam of light incident on the paraboloid is concentrated at the focal point. This applies also for other waves, hence parabolic antennas.