What is Mirrors: Definition and 255 Discussions

A mirror 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 aluminum are often used due to their high reflectivity, applied as a thin coating on glass because of its naturally smooth and very hard surface.
A mirror is a wave reflector. Light consists of waves, and when light waves reflect off the flat surface of a mirror, those waves retain the same degree of curvature and vergence, in an equal yet opposite direction, as the original waves. The light can also be pictured as rays (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 specular reflection, distinguishes a mirror from objects that diffuse 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 wavelength of the waves.
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 will yield 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 mirror is commonly used for inspecting oneself, such as during personal grooming; hence the old-fashioned name looking glass. This use, which dates from prehistory, overlaps with uses in decoration and architecture. Mirrors are also used to view other items that are not directly visible because of obstructions; examples include rear-view mirrors in vehicles, security mirrors in or around buildings, and dentist's mirrors. Mirrors are also used in optical and scientific apparatus such as telescopes, lasers, cameras, periscopes, and industrial machinery.
The terms "mirror" and "reflector" can be used for objects that reflect any other types of waves. An acoustic mirror reflects sound waves. Objects such as walls, ceilings, or natural rock-formations may produce echos, and this tendency often becomes a problem in acoustical engineering when designing houses, auditoriums, or recording studios. Acoustic mirrors may be used for applications such as parabolic microphones, atmospheric studies, sonar, and sea floor mapping. An atomic mirror reflects matter waves, and can be used for atomic interferometry and atomic holography.

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  1. H

    I Photon in a mirrored box moving in direction of travel

    Imagine a special box made of inward facing mirrors. These mirrors have zero mass and are perfectly reflective. A single photon is inside the box bouncing from side to side between the two mirrors of the sides of the box. The photon is perfectly preserved in this state, and loses no energy...
  2. elou

    B Light beams and their reflection

    I must add, that, when used in a lit space, or in daylight, spraying before the mirror does not make any light rays visible. Is it simply a matter of light scattering? Also, I am not sure whether this question belongs here or in classical physics.
  3. dykuma

    I Fabry-Perot Interferometer mirrors

    I am trying to build a Fabry-Perot interferometer to make some narrow band filters, and I was wondering if anyone can go into the specifics of whether there's anything special about the types of mirrors used in construction. I started by trying to see how hard it really is to make one on my...
  4. C

    Ray reflecting off intersecting mirrors

    For this problem, The solution is, I don't understand how if ## \gamma < 0## then there will be multiple reflections? I don't understand how ##\gamma## can be negative. Many thanks!
  5. N

    I Two mirrors to focus sunrays into a tiny spot -- possible?

    Hi guys, i am Nenad Komjenović from Bosnia and Herzegovina, I am just a regular guy, who likes geeky stuff and i don't know physics, so i wanted to ask you guys for an opinion. I was inspired by the "Markus Kayser - Solar Sinter Project" Youtube video, in which the guy used fresnel lens to...
  6. Father_Ing

    Two concave mirrors on a table

    I'm currently confused in determining whether an image formed by the 1st mirror (the left one) is a real or virtual object for the 2nd mirror. Here is the solution manual: This is what I have in my mind: Since the object is located between the focus and radius point of the first mirror, the...
  7. C

    I Do my parabolic mirrors need to be really shiny to reflect infrared?

    Summary:: Do my parabolic mirrors need to be really shiny to reflect infrared? I have 2 really old CENCO parabolic reflectors. I need to use them to demonstrate infrared light radiation by placing a heat source near one mirror, reflecting its heat to a second parabolic mirror and...
  8. A

    B Reactionless Drive Using Light Bouncing Off Moving Mirrors

    Here is a concept suggesting reactionless drive: Setup: A light pulse of wavelength l0 bouncing between 2 mirrors one on the left - ML and one on the right - MR. Each mirror oscillates perpendicularly to light travel direction attaining relativistic speeds vl, vr. Light pulse is timed so it...
  9. jaumzaum

    B Why we use spherical mirrors instead of parabolic mirrors?

    Parabolas are the only geometrical shape in which we have a perfect focus (not an approximate one) and does not depend in the angle of incidence being small. So, why do we even build spherical mirrors and not only parabolic mirros?
  10. G

    Optics question: Looking at mirrors from parallel to the surface

    I did a little experiment recently where I took a plane mirror and held it underneath a ceiling light. Then, I began to lower my head so that my view was closer and closer to the surface. When I did this, the image of the light began to drift lower and lower in the mirror until it completely...
  11. kspex2

    Two mirrors meet at a 135 degree angle.... (light ray question)

    I tried to use complementary angles and the law of reflection but I still have no idea how to find the angle.
  12. Vanilla Gorilla

    I Black Hole Bomb Effectiveness: Mirrors or Wormholes?

    For the Black Hole Bomb to be effective, does it need the mirrors there, or can they be replaced with wormholes, or some other quirk of spacetime?
  13. Sokolov

    Irradiance of light trapped between two parallel mirrors

    The setup of the problem is shown in the image below. I know that I must add all the contributions of each reflected ray and that its amplitude will be reduced by a factor ##r## each time it is reflected. So after the n-th reflection, its amplitude will be ##E_0r^n##, with ##E_0## the amplitude...
  14. M

    Heat Transfer - Radiation - Net heat transfer between two mirrors

    Hi, So there is already a written solution which I have, but this is more a question about why we omit reflection that come back to the same mirror? Method: Let us consider one of the mirrors, we know it will emit a heat flux given by: q_{1} = \epsilon_{1} \sigma T_{1}^4 . Given that we are...
  15. Addez123

    Lateral magnification in mirrors, simple issue

    The equation gives us that i = -mp = -0.4 * 30 = -12 The 'correct' answer is +12. Did I miss something here?
  16. NP04

    Magnification for Curved Mirrors

    Magnification |M|<1 = smaller |M|>1 = larger This is my reasoning because the magnification is -d0/di so it is the ratio that matters. Because wouldn't the sign just affect the type of image?? If you consider the sign in image size, you are saying that only one type of image (real/virtual)...
  17. F

    I Light pulse path, length and shape, when bouncing between two mirrors

    Hello, A light pulse moving bouncing between two mirrors (top and bottom) follows a vertical straight path w.r.t. to an inertial observer at rest relative to the mirrors. However, a moving inertial observer see the light pulse move in a zig-zag path as it bounced back and forth between the...
  18. Talisman

    I Mirrors, phase shifts, and position

    I'm confused about something regarding phase shifts but I'm not sure I've pinned down what. I had always thought of a mirror as introducing a global phase shift of π in the position basis, but I only now realize that this makes no sense: of course -A ⊗ B = A ⊗ -B, so a global phase shift is not...
  19. 4

    I Measuring Time with Mirrors: Exploring Special Relativity

    Special relativity is replete with examples of turning mirrors into clocks. Place two mirrors across from one another, bounce light between them, and measure the time. But as I thought about this, when a photon hits the mirror, it is absorbed by an electron which moves to a higher energy...
  20. Wrichik Basu

    How can this interesting set of mirrors be constructed?

    The mirror that I'm talking of, is situated in Hazarduari Palace in Murshidabad, West Bengal, India. This place was once the capital of Bengal under the Nawab before the British defeated the Nawab in the historic battle of Plassey, 1757. The history is not that important here, but the mirror...
  21. Erik Ayer

    I Is a Quantum-Controlled Mirror Possible?

    I was reading a pdf that mentioned a quantum-controlled beam splitter and wondered whether a quantum-controlled mirror exists. In the beam-splitter case, the beam splitter could either be present or absent, such that path information of photons was either preserved or not. It was controlled...
  22. B

    Making mirrors parallel in a vacuum using charge

    Two identical front surface mirrors are hung in a vacuum chamber with a high vacuum with a bit of bias of their mass wanting to lean into each other so they don't separate on their own. The metal surface is connected to a variable high voltage source. Both mirrors are connected to the same...
  23. H

    I Can Emission Theory Produce Doppler-Shift Formula?

    Emission theories propose that the velocity of light depends on the velocity of the light source. But the ordinary Doppler effect assumes the velocity of light remains as ##c## with respect to the ether medium, even when the light source is moving at speed ##v## with respect to the ether. They...
  24. U

    Do Concave Mirrors Always Form Real Images?

    i want to know the concave mirros is always real images or any difference then how to calculate thanks and regards Uday
  25. rkatcosmos

    Using multiple mirrors in Michelson Interferometer

    The number of mirrors typically used in Michelson Interferometer is 2. I am looking up the respective Wikipedia article and MIT's youtube video. I am wondering, for the sake of one of my experiment, whether more than 2 mirrors can be used in the interferometer? I require the traversing mirror...
  26. J

    Optics : How many images can be seen in inclined mirrors?

    Homework Statement Homework EquationsThe Attempt at a Solution [/B] I tried to draw a rough figure depicting the situation. Here M is the mosquito and I1, I2, I3 are its images . Mosquito can clearly see it's image I1 .Now whether it can see I2and I3 is something I am not too sure ...
  27. G

    I Why doesn't momentum transfer on mirrors reveal which path?

    Hi. In a Mach-Zehnder interferometer, there are mirrors in both paths. When a photon gets reflected on a mirror, it transfers momentum. Also, mirrors are classical objects that are usually not assumed to exist in superposition states. Shouldn't it (at least in principle) be possible to measure...
  28. I

    Placing object between 2 spherical mirrors

    Homework Statement A concave mirror (f1 = 13.6 cm) and a convex mirror (f2 = −7.00 cm) are facing each other and are separated by a distance of 35.8 cm. An object is placed between the mirrors and is 17.9 cm from each mirror. Consider the light from the object that reflects first from the...
  29. W

    Use of prisms vs use of mirrors in periscope

    Hi experts, I am aware using prisms enable total internal reflection while using mirrors there is only reflection of light. The difference is that in the former there is 100% light intensity after reflection while the latter does not. I have also read that using prisms is better than using...
  30. M

    Exploring Magnetic Mirrors in Fusion Reactors

    Hello! I hope that i am doing this right. This is my first post of a question. So, I've been reading about a design for a fusion reactor called a "Polywell". The Polywell, as I understand it, works by sending electron beams to the device's center which suck in protons/deuterium/tritium/etc. so...
  31. RabbitWho

    Understanding Focal Length: Solving for Image Position with 1/u + 1/v = 1/f

    Homework Statement u= distance from the object to the mirror v = distance from the image to the mirror f = focal length I don't understand what they are talking about and I would like to 2. Homework Equations If the image is real 1/u + 1 v = 1/f If the image is virtual 1/u - 1/v = 1/f The...
  32. P

    I 'If a photon were trapped between two perfect mirrors....'

    If a photon were trapped between two perfect mirrors perpendicular to its axis of motion, and they were gradually brought together until they were touching, so that the distance between their faces was 0m, would the photon be "trapped" between the mirrors? Without space in which to move, how...
  33. Erenjaeger

    Maximizing Telescope Sensitivity: The Importance of Mirror Size

    A telescopes sensitivity, or how much detail it can see is directly related to the size of the mirror area that collects light from the objects being observed. So a bigger mirror means higher resolution so you can see more detail at greater distances right? does it also mean it can collect more...
  34. G

    Proof of image formation property of spherical mirrors

    Hi. I'm trying to proof the image formation property of a concave spherical mirror. I know you can do this easily with a particular choice of rays (namely one that hits the vertex and one that passes through the center of the sphere) but I would like to show that a generic ray yields the same...
  35. A

    Find the distance from the mirrors for 4 reflections

    Homework Statement Two plain mirrors are put parallelly and 20 cm from each other. A source of light is put between the mirrors, 5 cm away from one. Find the distance from the mirrors of 4 first reflections. Homework Equations a1=a2 The distance of the object from the mirror and the reflection...
  36. F

    Can You Focus on Two Distances at Once?

    Homework Statement You are standing approximately 2 m away from a mirror. The mirror has water spots on its surface. True or False: It is possible for you to see the water spots and your image both in focus at the same time. Homework Equations p=object distance q=image distance The Attempt...
  37. D

    Recoil on mirrors and conservation of momentum

    I wanted to know whether or not a perfect mirror would experience recoil when light reflects off it, and I also wanted to know whether or not light can cause a recoil during total internal reflection. I suspect that the recoil is negligible (Even with a normal mirror) and that you could easily...
  38. Saleh0003

    What will happen -- Mirrors on the Moon to illunimate the Earth....

    if we fix huge amount of mirrors on surfface of moon...can we obtain light on Earth during night ?
  39. isnainidiah

    Fermat's Principle to explain lenses and mirrors

    How do we use Fermat's principle of least time to explain the required shapes of lenses and mirrors?
  40. Max Matiauda

    Image formed from object at focal point of concave mirror

    The question posed: "An object is located to the right of a mirror that in concave in its [the object's] direction. If the object sits on the focal point of the mirror, what answer best describes the image formed?" Our class is united in the notion that as the rays would be parallel...
  41. M

    Double slit experiment and mirrors

    Has the double slit experiment ever been performed with an adjacent reflection? With quantum weirdness I'm curious as to whether the reflection would give the same results as the actual apparatus as to which slit the particle wen through.
  42. M

    MHB What Are the Properties of Concave/Convex Spherical Mirrors?

    Spherical mirrors. We are given p= +18 and the mirror is concave with f= 12. Find r, i, m, Real or Virtual, Imaginary or not imaginary, and what side of the mirror is the image on. All units are cm. r: f=r/2, so r=2f r= 24 cm i: (1/p) + (1/i)= (1/f), so (1/f)-(1/p)=(1/i) i= 36 cm m...
  43. G

    Dichroic mirrors that reflect two wavelengths

    In fluorescence microscopy, dichroic mirrors reflect light under a critical wavelength (used to excite the sample) and transmit light over a critical wavelength (emission light from the sample). Are there mirrors that reflect two different wavelengths of light and transmit the rest? Essentially...
  44. K

    Angle of Deflection of Laser Given Tilted Mirror

    Hi Everyone, A question in my latest Physics I lab wishes for a proof showing that if a laser beam is incident on a mirror that is then rotated an angle θ the beam is deflected an angle 2θ. I attempted to prove this geometrically below. In the diagram the angle γ, is the angle of deflection...
  45. hxtasy

    Bounce light back and forth between mirrors forever?

    [Mentors' note - this post was forked off from this thread because it's an interesting question in its own right] I would also like clarification on this. if you throw a rubber ball at concrete, it will "bounce off". if you throw the rubber ball at mud, the mud will absorb it and it will stay...
  46. C

    Object Distance for Mirrors versus Lenses

    We are finishing up light and I'm a little confused on when the object distance would be negative when we are talking about mirrors and not lenses. The definition we were given is that the object distance is negative if the incoming light is on the opposite side of the mirror then the object is...
  47. unlimitedbacon

    Do parallel mirrors keep accelerating away from each other?

    Lets say you have two perfectly reflective parallel mirrors in a frictionless vacuum. You fire off a beam of light between them, so that it bounces between them continuously. Do they continuously accelerate away from each other due to radiation pressure? I think the answer must be no, but I...
  48. C

    What are the common methods for creating a laser point cloud?

    Hey all, I'm hoping this is in the right section. Basically I'm interested in creating a laser point cloud, but can't think of the best shape to do it. E.G. shining a laser straight down through a median and having the light scattered into a lot more points. I'd than have a receiver to read...
  49. B

    Question about concave mirrors

    I read that concave mirrors are part of a sphere, and concave mirrors can also be expressed in a parabola equation, but a parabola equation is expressed as #4py=x^2# and a circle as #x^2+y^2=R^2#. So the two can't be the same right? Can someone please explain this? Thank you in advance :)
  50. S

    Silvering of Plano-Convex Lens

    If the plane surface of a plano-convex lens in silvered then which of the following statements is true? 1. it acts like a convex mirror 2. it acts like a concave mirror 3. it acts like a concave lens 4. no changemy attempt--- the incident ray on the convex surface of the plano-convex will...