A mirror image is a reflected duplication that appears identical but in reverse. As an optical Optics is the branch of physics which studies the behavior and properties of light, including its interactions with matter and the construction of instruments that use or detect it. Optics usually describes the behavior of visible, ultraviolet, and infrared light. Because light is an electromagnetic wave, other forms of electromagnetic radiation effect it results from reflection Reflection is the change in direction of a wavefront at an interface between two different media so that the wavefront returns into the medium from which it originated. Common examples include the reflection of light, sound and water waves. The law of reflection says that for specular reflection the angle at which the wave is incident on the off of substances such as a mirror A mirror is a shiny object with at least one reflective surface. The most familiar type of mirror is the plane mirror, which has a flat surface. Curved mirrors are also used, to produce magnified or diminished images or focus light or simply distort the reflected image or water. It is also a concept in geometry Geometry "Earth-measuring" is a part of mathematics concerned with questions of size, shape, relative position of figures, and the properties of space. Geometry is one of the oldest sciences. Initially a body of practical knowledge concerning lengths, areas, and volumes, in the 3rd century BC geometry was put into an axiomatic form by and can also be used in a conceptualization process for 3-D structures.
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In geometry
In three dimensions
The concept of mirror image can be extended to three-dimensional Three-dimensional space is a geometric model of the physical universe in which we live. The three dimensions are commonly called length, width, and depth , although any three mutually perpendicular directions can serve as the three dimensions objects, including the inside parts, even if they are not transparent In the field of optics, transparency is the physical property of allowing light to pass through a material; translucency (also called translucence or translucidity) only allows light to pass through diffusely. The opposite property is opacity. Transparent materials are clear, while translucent ones cannot be seen through clearly. The term then relates to structural as well as visual aspects. This is also called enantiomer In chemistry, an enantiomer is one of two stereoisomers that are mirror images of each other that are "non-superposable" , much as one's left and right hands are "the same" but opposite. The term, pronounced /ɨˈnæntɪ.ɵmər/, is derived from the Greek ἐνάντιος, opposite, and μέρος, part or portion or enantiomorph.
If a point of an object has coordinates (x, y,z) then the image of this point (as reflected from the mirror in y, z plane) has coordinates (-x, y,z) - so mirror reflection is a reversal of the coordinate axis perpendicular to the mirror's surface. Thus, a mirror image does not have reversed right and left (or up and down), but rather reversed front and back. The left-right reversal of the mirror image only holds in relation a normal (i.e. unreflected) picture that we see in front of us; see schematic illustration at the right. For instance, if we look at a picture or object in our hand and then turn it towards a mirror, the picture and thus its mirror reflection have made a left-to-right 'flip over' of 180 degrees. The same principle holds when we stand with our back towards the mirror and face a picture or object in front of the mirror, and then compare it with its reflection by turning our head or body 180 degrees towards the mirror. It is thus not the mirror itself, but our own relative position and viewing point that has caused the apparent left-to-right reversal.
A mirror image appears three-dimensional if the observer moves. This is because the relative position of objects changes as the observer's perspective changes.[1]
Looking through a mirror from different positions (but necessarily with the point of observation restricted to the halfspace on one side of the mirror) is like looking at the 3D mirror image of space; without further mirrors only the mirror image of the halfspace before the mirror is relevant; if there is another mirror, the mirror image of the other halfspace is too.
Uses
The word fire and its mirror image are displayed on the front of this fire engine A fire apparatus, fire engine, fire truck, or fire appliance is a vehicle designed to assist in fighting fires by transporting firefighters to the scene and providing them with access to the fire, water or other equipment. In some areas, the terms fire engine and fire truck represent different types of fire fighting apparatusA text is sometimes deliberately displayed in mirror image, in order to be read through a mirror. Emergency vehicles such as ambulances An ambulance is a vehicle for transportation of sick or injured people to, from or between places of treatment for an illness or injury, and in some instances will also provide out of hospital medical care to the patient. The word is often associated with road going emergency ambulances which form part of an emergency medical service, or fire engines use mirror images in order to be read from a driver's rear-view mirror A rear-view mirror is a mirror in automobiles and other vehicles, designed to allow the driver to see rearward through the vehicle's backlight (rear windscreen). Some movie theaters Most movie theaters are commercial operations catering to the general public, who attend by purchasing a ticket. The movie is projected with a movie projector onto a large projection screen at the front of the auditorium. Some movie theaters are now equipped for digital cinema projection, removing the need to create and transport a physical film also use a Rear Window Captioning System to assist individuals with hearing impairments Hearing impairment or deafness refers to conditions in which individuals are fully or partially unable to detect or perceive at least some frequencies of sound which can typically be heard by members of their species. Use of the term impaired implies that deafness presents an inherent disadvantage to an animal, a view that is rejected within the watching the film.
Systems of mirrors
In the case of two mirrors, in planes at an angle α, looking through both from the sector which is the intersection of the two halfspaces, is like looking at a version of the world rotated by an angle of 2α; the points of observations and directions of looking for which this applies correspond to those for looking through a frame like that of the first mirror, and a frame at the mirror image with respect to the first plane, of the second mirror. If the mirrors have vertical edges then the left edge of the field of view is the plane through the right edge of the first mirror and the edge of the second mirror which is on the right when looked at directly, but on the left in the mirror image.
In the case of two parallel mirrors, looking through both once is like looking at a version of the world which is translated by twice the distance between the mirrors, in the direction perpendicular to them, away from the observer. Since the plane of the mirror in which one looks directly is beyond that of the other mirror, one always looks at an oblique angle, and the translation just mentioned has not only a component away from the observer, but also one in a perpendicular direction. The translated view can also be described by a translation of the observer in opposite direction. For example, with a vertical periscope A periscope is an instrument for observation from a concealed position. In its simplest form it consists of a tube with mirrors at each end set parallel to each other at a 45-degree angle. This form of periscope, with the addition of two simple lenses, served for observation purposes in the trenches during World War I. Military personnel also use, the shift of the world is away from the observer and down, both by the length of the periscope, but it is more practical to consider the equivalent shift of the observer: up, and backward.
See also
- relative direction The most common relative directions are left, right, forward, backward, up, and down. No absolute direction corresponds to any of the relative directions. This is a consequence of the translational invariance of the laws of physics: nature, loosely speaking, behaves the same no matter what direction one moves. As demonstrated by the Michelson-
- handedness Handedness is an attribute of humans defined by their unequal distribution of fine motor skill between the left and right hands. An individual who is more dexterous with the right hand is called right-handed, and one who is more skilled with the left is said to be left-handed. A minority of people are equally skilled with both hands, and are
- mirror writing
- flopped image
- flipped image
References
- ^ Adams, Cecil (1985-09-27). "Are dogs unable to see 2-D images (mirrors, photos, TV)?". The Straight Dope The Straight Dope is a popular question-and-answer newspaper column published in the Chicago Reader, syndicated in thirty newspapers in the United States and Canada, as well as being available and archived at the Straight Dope website. http://www.straightdope.com/classics/a2_071b.html. Retrieved 2008-01-31.
External links
- Why do mirrors reverse images left to right? Why not up and down?
- The same question explained a little differently, with examples
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Categories: Elementary geometry Elementary geometry consists of topics from geometry frequently taught at the primary or secondary school level | Chirality
