More Info on Mirrors
A mirror is a surface with good specular reflection that is smooth enough to form an image. The best known example is the plane mirror. The most common use is in the home for personal grooming but mirrors are also used in scientific apparatus such as telescopes and lasers, and in industrial machinery. Most of mirrors work with visible light, aiming the visual perception. However, the specular reflection of other waves also is used.
In Physics, mirrors are usually split into many groups, the two main groups are Curved Mirrors and Flat Mirrors, where curved mirrors include convex and concave mirrors. However, some people argue that a "flat mirror" is actually a curved mirror where its center of curviture is equal to infinity.
Effect
In a plane mirror, a parallel beam of light changes its direction as a whole, whilst still remaining parallel; the images formed by a plane mirror are virtual images, of the same size as the original object (see mirror image). There are also parabolic concave mirrors, where a parallel beam of light becomes a convergent beam, whose rays intersect in the focus of the mirror. Finally, there are convex mirrors, where a parallel beam becomes divergent, with the apparent intersection occurring behind the mirror. Note that spherical concave and convex mirrors do not have a single focal point, as often described in high school physics text books (see spherical aberration in lens (optics) and aberration in optical systems).
A beam of light reflects off a mirror at an angle of reflection that is equal to its angle of incidence. That is, if the beam of light is shining on a mirror's surface at a 30° angle from vertical, then it reflects from the point of incidence at a 30° angle from vertical in the opposite direction.
Composition
Early mirrors were usually a sheet of polished metal, often silver or copper, for example the Aranmula kannadi.
Most modern mirrors consist of a thin layer of aluminium deposited on a sheet of glass. They are back silvered, where the reflecting surface is viewed through the glass sheet; this makes the mirror durable, but lowers the image quality of the mirror due to extraneous reflections from the front surface of the glass. This type of mirror reflects about 80% of the incident light. The "back side" of the mirror is often painted black to completely seal the metal from corrosion.
Decoration
Mirrors, typically large and unframed, are frequently used in interior decoration to create an illusion of space, and amplify the apparent size of a room.
A decorative reflecting sphere of thin metal-coated glass, working as a reducing wide-angle mirror, is sold as a Christmas tree decoration called a bauble.
Signaling
With the sun as light source, a mirror can be used to signal, by variations in the orientation of the mirror. The signal can be used over long distances, possibly up to 60 kilometres on a clear day. This technique was used by Native American tribes and numerous militaries to transmit information between distant outposts.
Entertainment
The hall of mirrors, commonly found in amusement parks, is an attraction in which a number of distorted mirrors are used to produce unusual reflections of the visitor.
Mirrors are often used in magic to create an illusion.
Illuminated rotating disco balls covered with small mirrors are used to cast moving spots of light around a dance floor.
Source: Wikipedia
