A parabolic reflector (or dish or mirror) is a Parabola-shaped reflective device, used to collect or distribute energy such as light, sound, or radio waves. In Mathematics, the parabola (pəˈræbələ from the Greek παραβολή) is a Conic section, the intersection of a right circular A mirror is an object with a surface that has good Specular reflection; that is it is smooth enough to form an Image. In Physics and other Sciences energy (from the Greek grc ἐνέργεια - Energeia, "activity operation" from grc ἐνεργός Light, or visible light, is Electromagnetic radiation of a Wavelength that is visible to the Human eye (about 400–700 Sound' is Vibration transmitted through a Solid, Liquid, or Gas; particularly sound means those vibrations composed of Frequencies Radio waves are electromagnetic waves occurring on the Radio frequency portion of the Electromagnetic spectrum.
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Theory
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". In Geometry, the foci (singular focus) are a pair of special points used in describing Conic sections The four types of conic sections are the Circle Because many types of energy can be reflected in this way, parabolic reflectors can be used to collect and concentrate energy entering the reflector 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. Parabolic reflectors suffer from an aberration called coma. Aberrations are departures of the performance of an optical system from the predictions of Paraxial optics. In Optics (especially Telescopes, the coma (aka comatic aberration) in an optical system refers to aberration inherent to certain optical This is primarily of interest in telescopes because most other applications do not require sharp resolution off the axis of the parabola.
History
John Hadley introduced parabolic mirrors into practical astronomy in 1721 when he used one to build a reflecting telescope with very little spherical aberration. John Hadley ( April 16, 1682 Bloomsbury, London &ndash February 14, 1744, East Barnet, Hertfordshire Astronomy (from the Greek words astron (ἄστρον "star" and nomos (νόμος "law" is the scientific study A reflecting telescope (also called a reflector) is an Optical telescope which uses a single or combination of Curved mirrors that reflect Light spherical-aberration-diskjpg|thumb|300 px|left|A Point source as imaged by a system with negative (top zero (center and positive (bottom spherical aberration Before that, telescopes used spherical mirrors. "Globose" redirects here See also Globose nucleus. A sphere (from Greek σφαίρα - sphaira, "globe Lighthouses also commonly used parabolic mirrors to collimate a point of light from a lantern into a beam, before being replaced by more efficient fresnel lenses in the 19th century. A lighthouse is a Tower, building or framework designed to emit light from a system of lamps and lenses or in older times from a fire and used as an A Fresnel lens (pronounced or) is a type of lens invented by French physicist Augustin-Jean Fresnel.
Applications
The most common modern applications of the parabolic reflector are in satellite dishes, reflecting telescopes, radio telescopes, parabolic microphones, and many lighting devices such as spotlights, car headlights, PAR Cans and LED housings. A satellite dish is a type of Parabolic antenna that receives or transmits electromagnetic signals to and from another location typically a satellite A reflecting telescope (also called a reflector) is an Optical telescope which uses a single or combination of Curved mirrors that reflect Light A radio telescope is a form of directional Radio antenna used in Radio astronomy and in tracking and collecting data from Satellites A parabolic microphone is a Microphone that uses a Parabolic reflector to collect and focus Sound waves onto a receiver in much the same way that a " Electric Light " is a song by Infernal, scheduled to be their next single after " Whenever You Need Me " off their album Electric Stage lighting instruments are used in Stage lighting to illuminate theatrical productions rock Concerts A parabolic aluminized reflector luminare, or PAR light, is a Stage lighting fixture widely used in Theatre, Concerts and Motion picture
The Olympic Flame has been lit using a parabolic reflector concentrating sunlight. The Olympic Flame or Olympic Torch is a Symbol of the Olympic Games. Sunlight, in the broad sense is the total spectrum of the Electromagnetic radiation given off by the Sun. Parabolic mirrors are one of many shapes for a burning-glass. A burning-glass is a large convex lens that can concentrate the Sun 's rays onto a small area heating up the area and thus resulting in ignition of the
A parabolic reflector pointing upward can be formed by rotating a reflective liquid, like mercury, around a vertical axis. This makes the liquid mirror telescope possible. Liquid mirrors are Mirrors made with reflective liquids The most common liquid used is mercury, but other liquids will work as well (for example Low melting
A mirage bowl or parabolic mirror wok is a toy consisting of two parabolic mirrors that are put together like a wok pan and a lid with a hole in it. This article is about visual perception See Optical Illusion (Album for information about the Time Requiem album The device produces upright real image (with the magnification 1) of an object placed on the bottom of it, which gives the optical illusion that something is in the hole of the lid (while actually it is at the bottom of the pan below). In Optics, a real image is a representation of an actual object (source formed by rays of Light passing through the Image. Magnification is the process of enlarging something only in appearance not in physical size This article is about visual perception See Optical Illusion (Album for information about the Time Requiem album
Parabolic reflectors are a popular alternative for increasing wireless signal strength. Even with simple ones, users have reported 3 dB or more gains. [1]
See also
- Parabola
- Parabolic antenna
- Parabolic trough
- Paraboloid
- Spherical reflector
- Toroidal reflector
- Solar furnace
External links
- Java demonstration of a parabolic reflector
- Algorithm and spreadsheet for making a simple paraboloid: Design and make a paraboloid for use as a solar concentrator, sound mirror or microwave antenna. In Mathematics, the parabola (pəˈræbələ from the Greek παραβολή) is a Conic section, the intersection of a right circular The parabolic antenna is a high-gain reflector antenna used for radio television and data communications and also for radiolocation ( RADAR) on the UHF and A parabolic trough is a type of Solar thermal energy collector In Mathematics, a paraboloid is a Quadric surface of special kind A curved mirror is a Mirror with a curved reflective surface which may be either convex (bulging outward or concave (bulging inward A toroidal mirror is a form of Parabolic reflector which has a different focal distance depending on the angle of the mirror For the cooking apparatus see Solar cooker. For electricity generation see Solar updraft tower.
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