A mirror or looking glass is an object that reflects an image. Light that bounces off a mirror will show an image of whatever is in front of it, when focused through the lens of the eye or a camera. Mirrors reverse the direction of the image in an equal yet opposite angle from which the light shines upon it. This allows the viewer to see themselves or objects behind them, or even objects that are at an angle from them but out of their field of view, such as around a corner. Natural mirrors have existed since prehistoric times, such as the surface of water, but people have been manufacturing mirrors out of a variety of materials for thousands of years, like stone, metals, and glass. In modern mirrors, metals like silver or aluminium are often used due to their high reflectivity, applied as a thin coating on glass because of its naturally smooth and very hard surface.
[Extra Quality] Behind The Mirro
When looking at a mirror, one will see a mirror image or reflected image of objects in the environment, formed by light emitted or scattered by them and reflected by the mirror towards one's eyes. This effect gives the illusion that those objects are behind the mirror, or (sometimes) in front of it. When the surface is not flat, a mirror may behave like a reflecting lens. A plane mirror yields a real-looking undistorted image, while a curved mirror may distort, magnify, or reduce the image in various ways, while keeping the lines, contrast, sharpness, colors, and other image properties intact.
A convex parabolic mirror, on the other hand, will reflect rays that are parallel to its axis into rays that seem to emanate from the focus of the surface, behind the mirror. Conversely, it will reflect incoming rays that converge toward that point into rays that are parallel to the axis. A convex mirror that is part of a prolate ellipsoid will reflect rays that converge towards one focus into divergent rays that seem to emanate from the other focus.[43]
For things that may be considered as two-dimensional objects (like text), front-back reversal cannot usually explain the observed reversal. An image is a two-dimensional representation of a three-dimensional space, and because it exists in a two-dimensional plane, an image can be viewed from front or back. In the same way that text on a piece of paper appears reversed if held up to a light and viewed from behind, text held facing a mirror will appear reversed, because the image of the text is still facing away from the observer. Another way to understand the reversals observed in images of objects that are effectively two-dimensional is that the inversion of left and right in a mirror is due to the way human beings perceive their surroundings. A person's reflection in a mirror appears to be a real person facing them, but for that person to really face themselves (i.e.: twins) one would have to physically turn and face the other, causing an actual swapping of right and left. A mirror causes an illusion of left-right reversal because left and right were not swapped when the image appears to have turned around to face the viewer. The viewer's egocentric navigation (left and right with respect to the observer's point of view; i.e.: "my left...") is unconsciously replaced with their allocentric navigation (left and right as it relates another's point of view; "...your right") when processing the virtual image of the apparent person behind the mirror. Likewise, text viewed in a mirror would have to be physically turned around, facing the observer and away from the surface, actually swapping left and right, to be read in the mirror.[44]
Mirrors can be manufactured to a wide range of engineering tolerances, including reflectivity, surface quality, surface roughness, or transmissivity, depending on the desired application. These tolerances can range from wide, such as found in a normal household-mirror, to extremely narrow, like those used in lasers or telescopes. Tightening the tolerances allows better and more precise imaging or beam transmission over longer distances. In imaging systems this can help reduce anomalies (artifacts), distortion or blur, but at a much higher cost. Where viewing distances are relatively close or high precision is not a concern, wider tolerances can be used to make effective mirrors at affordable costs.
Telescopes and other precision instruments use front silvered or first surface mirrors, where the reflecting surface is placed on the front (or first) surface of the glass (this eliminates reflection from glass surface ordinary back mirrors have). Some of them use silver, but most are aluminium, which is more reflective at short wavelengths than silver.All of these coatings are easily damaged and require special handling.They reflect 90% to 95% of the incident light when new.The coatings are typically applied by vacuum deposition.A protective overcoat is usually applied before the mirror is removed from the vacuum, because the coating otherwise begins to corrode as soon as it is exposed to oxygen and humidity in air. Front silvered mirrors have to be resurfaced occasionally to maintain their quality. There are optical mirrors such as mangin mirrors that are second surface mirrors (reflective coating on the rear surface) as part of their optical designs, usually to correct optical aberrations.[66]
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From the earliest recorded history, humans have been fascinated by reflections. Narcissus was supposedly bewitched by his own reflection in a pool of water, and magic powers are ascribed to mirrors in fairy tales. Mirrors have advanced from reflective pools and polished metal surfaces to clear glass handheld and bathroom mirrors. They have been used in interior decoration since the 17th century, and reflective surfaces on cars and in hotel lobbies are still popular in modern design. Mirrors are used for practical purposes as well: examining our appearance, examining what is behind us on the road, building skyscrapers, and making scientific research instruments, such as microscopes and lasers.
Materials technology drastically affects the quality of a mirror. Light reflects best from surfaces that are non-diffusive, that is, smooth and opaque, rather than transparent. Any flaw in this arrangement will detract from the effectiveness of the mirror. Innovations in mirror making have been directed towards flattening the glass used and applying metal coatings of uniform thickness, because light traveling through different thicknesses of glass over different parts of a mirror results in a distorted image. It is due to these irregularities that some mirrors make you look thinner and some fatter than normal. If the metal backing on a mirror is scratched or thin in spots, the brightness of the reflection will also be uneven. If the coating is very thin, it may be possible to see through the mirror. This is how one-way mirrors are made. Non-opaque coating is layered over the thin, metal backing and only one side of the mirror (the reflecting side) is lit. This allows a viewer on the other side, in a darkened room, to see through.
These base materials must be coated to make a mirror. Metallic coatings are the most common. A variety of metals, such as silver, gold, and chrome, are appropriate for this application. Silver was the most popular mirror backing one hundred years ago, leading to the coinage of the term "silvering." Old silver-backed mirrors often have dark lines behind the glass, however, because the material was coated very thinly and unevenly, causing it to flake off, scratch or tarnish. More recently, before 1940, mirror manufacturers used mercury because it spread evenly over the surface of the glass and did not tarnish. This practice was also eventually abandoned, for it posed the problem of sealing in the toxic liquid. Today, aluminum is the most commonly used metallic coating for mirrors.
Batch mirror uniformity is the first and fore-most job of quality assurance. Mirrors on the edge of a grinding plate or evaporator chamber may not have the same surface or coating as those in the center of the apparatus. If there is a wide range of metal thicknesses or surface flatnesses in a single batch of mirrors, the process must be adjusted to improve uniformity.
Several methods are employed to test the integrity of a mirror. The surface quality is examined first visually for scratches, unevenness, pits, or ripples. This can be done with the unaided eye, with a microscope, or with an infrared photographic process designed to show differences in metal thicknesses.
Background The reason why you see objects is that light hitting these objects reflects back into your eyes (and then is perceived and represented as those objects by your brain). But what happens if light coming from an object hits a flat mirror and is reflected (or bounced back) before it hits your eyes? Your brain, being unaware that the light was reflected, will reconstruct an image with the information it received, assuming the light traveled on a straight path from the object to the eye. The result is what you see in the mirror: an object that looks similar, but appears to be placed behind the mirror. We call this a reflection of the object. It is an optical illusion, a virtual image of a real object. 2ff7e9595c
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