Everything about Parabolic Mirror totally explained
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.
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's 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 reflector at a particular angle. Similarly, energy radiating from the "focus" to the dish can be transmitted outward in a beam that's parallel to the axis of the dish. Parabolic reflectors suffer from an
aberration called
coma. This is primarily of interest in telescopes because most other applications don't 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. Before that, telescopes used
spherical mirrors.
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.
Applications
The most common modern applications of the parabolic reflector are in
satellite dishes,
telescopes (including radio telescopes),
parabolic microphones, and many
lighting devices such as
spotlights,
car headlights,
PAR Cans and LED housings.
The
Olympic Flame has been lit using a parabolic reflector concentrating
sunlight. Parabolic mirrors are one of many shapes for a
burning-glass.
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.
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. 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's at the bottom of the pan below).
Parabolic reflectors are a popular alternative for increasing wireless signal strength. Even with simple ones, users have reported 3 dB or more gains.
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