question: Why can't near-sighted people see reflections of far-away objects, even when the mirror is close up?
comment: The issue with nearsightedness (and similar ailments) is that the lens in the eye isn't focusing properly, which is to say it isn't making sure light only from a specific angle is falling on a given part of the retina. Reflected light retains the angle at which it arrived at the surface when it is reflected, meaning that the focus problems with the eye are still retained.
passages: In severe cases of hyperopia from birth, the brain has difficulty in merging the images that each individual eye sees. This is because the images the brain receives from each eye are always blurred. A child with severe hyperopia can never see objects in detail. If the brain never learns to see objects in detail, then there is a high chance of one eye becoming dominant. The result is that the brain will block the impulses of the non-dominant eye. In contrast, the child with myopia can see objects close to the eye in detail and does learn at an early age to see detail in objects.
   Plane mirrors are the only type of mirror for which a real object always produces an image that is virtual, erect and of the same size as the object. Virtual objects produce real images, however. The focal length of a plane mirror is infinity; its optical power is zero.
  
  Section::::Preparation.
   Section::::Classification.
  
  An eye that has no refractive error when viewing distant objects is said to have "emmetropia" or be "emmetropic" meaning the eye is in a state in which it can focus parallel rays of light (light from distant objects) on the retina, without using any accommodation. A distant object in this case is defined as an object located beyond 6 meters, or 20 feet, from the eye, since the light from those objects arrives as essentially parallel rays when considering the limitations of human perception.
   In scenes where a bright object is next to a faint object, veiling glare from the bright object may hide the faint object from view, even though the instrument is otherwise capable of spatially resolving the two. Veiling glare is a limiting factor in high-dynamic-range imaging.
  
  Glare in optical instruments differs from glare in vision, even though they both follow the same physical principles, because the phenomenon arises from mechanical versus physiological features.
  
  Section::::Factors and design techniques.
   BULLET::::- A plane mirror forms a virtual image positioned behind the mirror. Although the rays of light seem to come from behind the mirror, light from the source only exists in front of the mirror. The image in a plane mirror is not magnified (that is, the image is the same size as the object) and appears to be as far behind the mirror as the object is in front of the mirror.
   One can observe the effect of straylight by looking at a distant bright light source against a dark background. If the source is small, it would look like a small bright spot if the eye imaged it perfectly. Scattering in the eye makes the source appear spread out, surrounded by glare. The disability glare caused by such a situation has been found to correspond precisely to the effect of true light. As a consequence, disability glare was subsequently defined by this true light, called "straylight".
  
  Section::::Individual differences.
   When light strikes an interface between two materials, the reflected light is generally partially polarized. However, if the light strikes the interface at Brewster's angle, the reflected light is "completely" linearly polarized parallel to the interface. Brewster's angle is given by
  
  Section::::Consequences.:Reflected images.
  
  The image in a flat mirror has these features:
  
  BULLET::::- It is the same distance behind the mirror as the object is in front.
  
  BULLET::::- It is the same size as the object.
  
  BULLET::::- It is the right way up (erect).
  
  BULLET::::- It is reversed.
   There is at least one vertebrate, the spookfish, whose eyes include reflective optics for focusing of light. Each of the two eyes of a spookfish collects light from both above and below; the light coming from above is focused by a lens, while that coming from below, by a curved mirror composed of many layers of small reflective plates made of guanine crystals.
  
  Section::::Types.:Compound eyes.
   BULLET::::- Purkinje images are the reflections from the anterior and posterior surfaces of the cornea and the anterior and posterior surfaces of the lens. While these first four reflections are not entoptic, Becker described how light can reflect from the posterior surface of the lens and then again from the anterior surface of the cornea to focus a second image on the retina, this one much fainter and inverted. Tscherning referred to this as the sixth image (the fifth image being formed by reflections from the anterior surfaces of the lens and cornea to form an image too far in front of the retina to be visible) and noted it was much fainter and best seen with a relaxed emmetropic eye. In a dark room, with one eye closed and looking ahead with the other eye, move a light back and forth under your gaze – you should see a dimmer image moving in the opposite direction.
   In the U.S. and Canada, the U.S. National Highway Traffic Safety Administration's Federal Motor Vehicle Safety Standard 111 and the Canada Motor Vehicle Safety Standard 111 require the driver side mirror to provide "unit magnification", i.e., an undistorted 1:1 reflection achieved with a flat mirror. However, unit magnification limits the field of view that can be provided by a mirror of size compatible with the vehicle body. The ECE regulations in use throughout most of the world except North America permit the driver side mirror to have a planar, convex, or aspheric surface; an aspheric section is often combined with a larger convex section, and the two sections are separated by a visible line to alert the driver to the two sections' different perspective shifts.
   Hero demonstrated the equality of the angle of incidence and reflection on the grounds that this is the shortest path from the object to the observer. On this basis, he was able to define the fixed relation between an object and its image in a plane mirror. Specifically, the image appears to be as far behind the mirror as the object really is in front of the mirror.
   Few materials do not cause diffuse reflection: among these are metals, which do not allow light to enter; gases, liquids, glass, and transparent plastics (which have a liquid-like amorphous microscopic structure); single crystals, such as some gems or a salt crystal; and some very special materials, such as the tissues which make the cornea and the lens of an eye. These materials can reflect diffusely, however, if their surface is microscopically rough, like in a frost glass (Figure 2), or, of course, if their homogeneous structure deteriorates, as in cataracts of the eye lens.
   Far-sightedness is often present from birth, but children have a very flexible eye lens, which helps to compensate. In rare instances hyperopia can be due to diabetes, and problems with the blood vessels in the retina.
  
  Section::::Diagnosis.
  
  A diagnosis of far-sightedness is made by utilizing either a retinoscope or an automated refractor-objective refraction; or trial lenses in a trial frame or a phoropter to obtain a subjective examination. 
  
  Ancillary tests for abnormal structures and physiology can be made via a slit lamp test, which examines the cornea, conjunctiva, anterior chamber, and iris.
   Internal reflections, sometimes called "scatter", cause the light passing through an eyepiece to disperse and reduce the contrast of the image projected by the eyepiece. When the effect is particularly bad, "ghost images" are seen, called "ghosting". For many years, simple eyepiece designs with a minimum number of internal air-to-glass surfaces were preferred to avoid this problem.
   The term "optical wedge" refers to any shallow angle between two plane surfaces of a window. This wedge may range from a few millionths of a degree of perfect parallelism to as much as three degrees of angle. Even though high-precision optics, such as optical flats, may be lapped and polished to extremely high levels of parallelism, nearly all optics with parallel faces have some slight wedge. This margin of error is usually listed in minutes or seconds of arc. Windows manufactured with an intentional wedge are often referred to as wedge prisms, and typically come with wedge angles of one, two, or three degrees. Many applications exist for wedge prisms, including laser-beam steering, rangefinding and variable focusing.
   Light strays or scatters in lenses due to many potential factors in design and operation. These factors include dirt, film, or scratches on lens surfaces; reflections from lens surfaces or their mounts; and the slightly imperfect transparency (or reflection) of real glass (or mirrors).
  
  Typical optical engineering design techniques to minimize stray light include: black coatings on internal surfaces, knife edges on mounts, antireflection lens coatings, internal baffles and stops, and tube extensions which block sources outside the field of view.
   The brownsnout spookfish is a species of barreleye is the only vertebrate known to employ a mirror, as opposed to a lens, to focus an image in its eyes.
   A surface can therefore appear very shiny if it has a well-defined specular reflectance at the specular angle. The perception of an image reflected in the surface can be degraded by appearing unsharp, or by appearing to be of low contrast. The former is characterised by the measurement of the distinctness-of-image and the latter by the haze or contrast gloss.
  
  In his paper Hunter also noted the importance of three main factors in the measurement of gloss:
  
  BULLET::::- The amount of light reflected in the specular direction
   Different processes can lead to opacity including absorption, reflection, and scattering.
  
  Section::::Radiopacity.
   Section::::Stereo vision.:Challenging earlier views.
   As the FSM mirror is optically flat, FSM's need not be located at pupil images. Two FSM's can be combined to create an anti-beamwalk pair, which stabilizes not only the beam pointing angle but the location of the beam center. Anti-beamwalk FSM's are positioned prior to a deformable mirror (which must be located at a pupil image) to stabilize the position of the pupil image on the deformable mirror and minimize correction errors resulting from wavefront movement, or shearing, on the deformable mirror faceplate.
  
  Section::::References.
  
  BULLET::::- Malacara, D., "Optical Shop Testing - Second Edition", John Wiley and Sons, 1992, .
   For small telescopes using spherical mirrors with focal ratios shorter than "f"/10, light from a distant point source (such as a star) is not all focused at the same point. Particularly, light striking the inner part of the mirror focuses farther from the mirror than light striking the outer part. As a result, the image cannot be focused as sharply as if the aberration were not present. Because of spherical aberration, telescopes with focal ratio less than "f"/10 are usually made with non-spherical mirrors or with correcting lenses.
   Reflecting telescopes, just like any other optical system, do not produce "perfect" images. The need to image objects at distances up to infinity, view them at different wavelengths of light, along with the requirement to have some way to view the image the primary mirror produces, means there is always some compromise in a reflecting telescope's optical design.
   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.
  
  Section::::In geometry and geometrical optics.:In three dimensions.:Effect of mirror on the lighting of the scene.
   Section::::Sources.:Lenses and mirrors.
  
  A perfect parabolic mirror will bring parallel rays to a focus at a single point. Conversely, a point source at the focus of a parabolic mirror will produce a beam of collimated light creating a Collimator. Since the source needs to be small, such an optical system cannot produce much optical power. Spherical mirrors are easier to make than parabolic mirrors and they are often used to produce approximately collimated light. Many types of lenses can also produce collimated light from point-like sources.
  
  Section::::Sources.:Display system in flight simulators that uses collimated light.
  
presuppositions: Distance causes near-sightedness.  Near sighted people should be able to see reflections of far objects if the mirror is held close to them.
corrections: Light angle causes near-sightedness, not distance.  In near sighted people, the lens of the eye isn't focusing properly, therefore the light does not reach every part of the retina which prevents them from being able to see reflections of distant objects.
raw_presuppositions: Distance causes near-sightedness.  Near sighted people should be able to see reflections of far objects if the mirror is held close to them. Near sighted people should be able to see reflections of far objects
raw_corrections: Light angle causes near-sightedness, not distance.  In near sighted people, the lens of the eye isn't focusing properly, therefore the light does not reach every part of the retina which prevents them from being able to see reflections of distant objects. That isnt how light works. 