Satellite antennas use parabolic reflectors to focus energy.
A parabolic mirror is a mirror that is shaped like a parabolic bowl. Parabolic mirrors are symmetric in two directions about their major axis (i.e., the line that passes through the "middle" of the bowl and through the parabolic vertex).
Curved vs. Flat Mirrors
Flat mirrors produce virtual images, meaning that the image appears as a reflection and is "located" behind the mirror. Light rays from the object bounce off the mirror and travel back toward the object in a straight line.
Curved mirrors reflect the rays that travel parallel to the mirror's major axis of symmetry, at an angle such that they converge at a focal point in front of the mirror on the major axis.
The Focus
The focus, or focal point, of a curved mirror is the point where rays converge, following their angular reflection from the surface of the mirror. At this convergence point, a curved mirror can render an image from a distant object, or collect energy for transmission applications.
Parabolic mirrors---which are curved more drastically than spherical mirrors---are ideally suited for these purposes, because they can be engineered to focus energy very narrowly during collection or transmission.
Uses of Parabolic Mirrors
Parabolic mirrors are the primary components of telescopes and satellite dishes. They are integral to reflecting telescopes, such as the orbiting Hubble Space Telescope, which is the backbone of one of NASA's most successful space missions. Parabolic reflectors are also essential components of most radio telescopes, spacecraft tracking programs, and space-to-ground communication systems.
The satellites that orbit Earth to provide satellite-based services such as DishTV, satellite radio and global positioning systems also rely on large parabolic reflectors, which focus beams of energy for transmission back toward the surface of the planet.
Tags: major axis, back toward, curved mirror, energy transmission, focal point
