Mirror

A mirror, also known as a looking glass, is an object that <a href="/facts/Reflection_(physics)/BhcjDs79">reflects</a> an <a href="/facts/Image/hbjEdTXK">image</a>. Light that bounces off a mirror forms an image of whatever is in front of it, which is then focused through the lens of the eye or a camera. Mirrors reverse the direction of light at an angle equal to its incidence. 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 <a href="/facts/Prehistory/52D6oKM4">prehistoric</a> 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 <a href="/facts/Silver/xXe41BGg">silver</a> or <a href="/facts/Aluminium/7wmR8jYE">aluminium</a> are often used due to their high <a href="/facts/Reflectivity/TT4sBwIw">reflectivity</a>, applied as a thin coating on <a href="/facts/Glass/hezRsAGf">glass</a> because of its naturally smooth and very <a href="/facts/Hardness_(materials_science)/PtGn6E20">hard</a> surface.
A mirror is a <a href="/facts/Wave_(physics)/I3EeyInV">wave</a> reflector. <a href="/facts/Light/jeofpMn4">Light</a> consists of waves, and when light waves reflect from the flat surface of a mirror, those waves retain the same degree of curvature and <a href="/facts/Vergence_(optics)/NVQ2Xmcs">vergence</a>, in an equal yet opposite direction, as the original waves. This allows the waves to form an image when they are focused through a lens, just as if the waves had originated from the direction of the mirror. The light can also be pictured as <a href="/facts/Ray_(optics)/PgUEC7Sm">rays</a> (imaginary lines radiating from the light source, that are always perpendicular to the waves). These rays are reflected at an equal yet opposite angle from which they strike the mirror (incident light). This property, called <a href="/facts/Specular_reflection/dwVIqLVb">specular reflection</a>, distinguishes a mirror from objects that <a href="/facts/Diffuse_reflection/wG9w4tAX">diffuse</a> light, breaking up the wave and scattering it in many directions (such as flat-white paint). Thus, a mirror can be any surface in which the texture or roughness of the surface is smaller (smoother) than the <a href="/facts/Wavelength/kcJU0ymz">wavelength</a> of the waves.
When looking at a mirror, one will see a <a href="/facts/Mirror_image/xkbUhBzI">mirror image</a> 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) <a href="/facts/Real_image/G8KApAFz">in front of it</a>. When the surface is not flat, a mirror may behave like a reflecting <a href="/facts/Lens/ejlH6n5c">lens</a>. A <a href="/facts/Plane_mirror/dLG3UepS">plane mirror</a> yields a real-looking undistorted image, while a <a href="/facts/Curved_mirror/X1c0aVmK">curved mirror</a> may distort, magnify, or reduce the image in various ways, while keeping the lines, <a href="/facts/Contrast_(vision)/zD9F91Je">contrast</a>, <a href="/facts/Sharpness_(visual)/xgE5cm2N">sharpness</a>, colors, and other image properties intact.
A mirror is commonly used for inspecting oneself, such as during <a href="/facts/Personal_grooming/764poF85">personal grooming</a>; hence the old-fashioned name "looking glass". This use, which dates from prehistory, overlaps with uses in <a href="/facts/Decorative_arts/w0TpPKvu">decoration</a> and <a href="/facts/Architecture/FccThs8G">architecture</a>. Mirrors are also used to view other items that are not directly visible because of obstructions; examples include <a href="/facts/Rear-view_mirror/VfPbP3gl">rear-view mirrors</a> in vehicles, <a href="/facts/Curved_mirror/X1c0aVmK">security mirrors</a> in or around buildings, and <a href="/facts/Mouth_mirror/bsodM9zw">dentist's mirrors</a>. Mirrors are also used in optical and scientific apparatus such as <a href="/facts/Telescope/BDwYahhR">telescopes</a>, <a href="/facts/Laser/jk6PTvvT">lasers</a>, <a href="/facts/Camera/j4uqsfJQ">cameras</a>, <a href="/facts/Periscope/jSCoMFnw">periscopes</a>, and industrial machinery.
According to <a href="/facts/Superstition/XB63u3qt">superstitions</a> breaking a mirror is said to bring seven years of <a href="/facts/List_of_bad_luck_signs/xgMYdFI2">bad luck</a>.
The terms "mirror" and "reflector" can be used for objects that reflect any other types of waves. An <a href="/facts/Acoustic_mirror/GmkBudpI">acoustic mirror</a> reflects sound waves. Objects such as walls, ceilings, or natural rock-formations may produce <a href="/facts/Echo/MCYU8q1S">echos</a>, and this tendency often becomes a problem in <a href="/facts/Acoustical_engineering/oSIa0pwR">acoustical engineering</a> when designing houses, auditoriums, or recording studios. Acoustic mirrors may be used for applications such as <a href="/facts/Parabolic_microphone/MKtzQKAF">parabolic microphones</a>, <a href="/facts/Atmosphere/oUpLaGRF">atmospheric</a> studies, <a href="/facts/Sonar/0Rg2G40e">sonar</a>, and <a href="/facts/Seafloor_mapping/r7MCus78">seafloor mapping</a>. An <a href="/facts/Atomic_mirror/usmysDRM">atomic mirror</a> reflects <a href="/facts/Matter_waves/Rpszb8f1">matter waves</a> and can be used for atomic <a href="/facts/Interferometry/X3E1SsQT">interferometry</a> and atomic <a href="/facts/Holography/4J1gW0M6">holography</a>.

Mirror open-in-new

Mirror