A parabolic reflector (also known as a parabolic dish or a parabolic mirror) is a reflective device formed in the shape of a paraboloid of revolution. Parabolic reflectors can either collect or distribute energy such as light, sound, or radio waves.
The parabolic reflector functions due to the geometric properties of the paraboloid shape: if the angle of incidence to the inner surface of the collector equals the angle of reflection, then any incoming ray that is parallel to the axis of the dish will be reflected to a central point, or "focus". Because many types of energy can be reflected in this way, parabolic reflectors can be used to collect and concentrate energy entering the relector at a particular angle. Similarly, energy radiating from the "focus" to the dish can be transmitted outward in a beam that is parallel to the axis of the dish.
Isaac Newton introduced parabolic mirrors into practical astronomy when he invented the reflecting telescope. The most common applications of the parabolic reflector are in satellite dishes, telescopes (including radio telescopes), parabolic microphones and many lighting devices such as spotlights, car headlights and LED housings.
Parabolic reflectors suffer from an aberration called coma. This is only of interest in telescopes because other applications don't require sharp resolution off the axis of the parabola.
The Olympic Flame is lit using a parabolic reflector concentrating sunlight.
See also