What is Mirror: Definition and 652 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. X

    I DIY Helmet Mounted HUD

    Hello, I'm trying to build a helmet-mounted display. Basically a HUD that is contained fully within a helmet. I am not experienced with optics though and can only sift through what the internet has to offer. I don't want it to be a "put your phone down next to an angled piece of polycarbonate"...
  2. F

    Magnetic mirror end plug

    Hello, Knowing that the loss cone for a symmetrical geometry is also symmetrical, I was thinking has anyone ever tried a magnetic mirror where the central magnets are circular but the end magnets that create the highest B field are instead flattened. Wouldn't a flat coil achieve a stronger B...
  3. S

    I Questions about a Laser Interferometer pattern

    Is it possible to get an interference pattern if the original laser beam is not splitted before reunited? Can I use 2 mirrors which will be separated 2 cm from each other and they reflect the light from the incident ray 500 meter far which is then reunited to get an interference pattern on a...
  4. P

    Please explain this mirror

    The following photo was taken of a mirror in my hotel room in Dublin, Ireland a month ago. This mirror has two individual panes, I assume silvered differently. Why? Is the magnification of the left pane intentional, a mounting effect or a consequence? I appreciate whatever you may have to...
  5. Z

    B Speed of Light Reflection: Einstein's Train & Mirrors

    Hello Let's suppose we have 2 observers. One is in Einstein's train and one is outside. There are 2 mirrors: one inside the train and one outside. Speed of train is v Both observers emit light which reflects from both mirrors. What will be the speed of reflected light for both observers from...
  6. M

    Concave mirror reflecting a point lamp, that create a wider beam

    I've look if there was any way to get the "image size" or a ratio to use the Mirror Equation to find the focal length, but nothing. I think it's base on some geometry, but I don't see the relation.
  7. I

    I Mirror rotates any polarisation by 90°?

    Over each eye is a linear polariser and they are orthogonal to each other. So I conclude from the experiment that the polarisation must have been rotated by 90° by the mirror. That reminded my of phase plates but they only work because their refractive indix depends on the angle. Along two...
  8. A

    B Color of a mirror on the Earth

    If I place a mirror on the ground facing upward, what color will those who observe it from space see?
  9. gmax137

    FB and youtube videos -- mirror imaging

    Does anyone know why this mirror imaging happens?
  10. Melbourne Guy

    Focal length of LCD screen as a car's rear view mirror

    I noticed on the commute home today a car with a LCD rear view mirror and I wondered whether, if I were driving it, I'd be able to focus on it the same as I focus on my car's glass review view mirror? I need glasses to read, and that includes a computer, so figured a LCD screen that close, even...
  11. GhostLoveScore

    B Effect of JWST mirror damage on final images

    As most of us know, James Webb Space Telescope suffered a damage to one of its mirror segments due to meteoroid impact. How will that damage show in the images? Some people on certain forum I visit say that there will be some artifacts visible in only one part of the image, but that doesn't...
  12. rishurboi

    I Applications of Virtual objects

    I've heard virtual objects are used in cinema halls I'm not sure of what that means, can someone explain this to me please? And btw by virtual object i mean when diverging rays from real object passes through a convex lens, the rays will converging and if you'll place a plane mirror infront of...
  13. S

    Can twin cats have mirror image fur colors?

    Is it possible for monozygotic twin cats to have fur colors that are mirror images of each other? Or does such mirror imaging rule out that two cats are monozygotic twins? In searching for images of "twin cats" on the web, I find a few photos of pairs that have mirror image fur colors. For...
  14. mcas

    Evaluate reflectance of an aluminum mirror

    Note: for some reason frequency on this lecture is indicated by \omega. I wanted to calculate the reflectance using one of these equations that were given to us during the lecture: R=1 where \omega < \omega_p...
  15. H

    Lawn/Garden Convex Mirror in Backyard to reflect sunlight onto the house

    Hello- I am starting a project to get direct sunlight onto the house by placing convex mirrors on the outside stone fence of the backyard since it is the only place of my property that is not shaded by other houses in the neighborhood. For that, I need to calculate the size of the mirrors...
  16. P

    How does mirror symmetry for resistance work?

    The question is to find the resistance between AF (top 2 points). Let the far right unlabelled vertex of the pentagon be B. Why can we say that points O and C are at the same potential? I get that both points O and C appear to be at 'half the path' if you consider AOF and ABCDF, and so potential...
  17. A

    What Causes Loss of Particles in a Magnetic Mirror?

    If I am not mistaken (hopefully) then the highest loss through the mirror ends in a magnetic mirror happens with particles that have a higher parallel component to the field lines than a higher perpendicular (gyro frequency). In a magnetic mirror if we map these properties onto the real physical...
  18. Ebi Rogha

    I Can a single photon be reflected by a mirror?

    If the answer is Yes, then I would ask, if the mirror absorbs a portion of the energy of the photon, so the photon should simply stop existing because we cannot have a smaller package of light than a photon. If the answer is No, then I would ask why a beam of light (which is made of a big...
  19. Jarvis323

    Optical Ideas for Infinity Mirror Geometries

    I'd like to make a large scale infinity dodecahedron, or icosahedron, or something similar. I'm just curious if anyone around here has an idea for a different/more complicated geometry that would work well?
  20. J

    Mirror coating and BSDF measurement costs?

    I need an epoxy/polycarbonate substrate diffuser film similar to this one https://www.luminitco.com/products/light-shaping-diffusers mirror and hard coated. I have two films sized 100x100mm each (3.93x3.93 inches or 5.57'' diagonal ). I have no idea what this will cost. What's the expected...
  21. Mr_Allod

    Reflection and Refraction in an Elliptical Imaging Mirror

    My thoughts so far: a. Since the critical angle occurs at the origin for the given parameters I would imagine that the maximum power reflected would be 100% since at the critical angle ##\theta_t = \frac \pi 2## and ##r_ {\perp} = r_{\parallel} = 1##. I do not know how I might go about finding...
  22. N

    Virtual and real image with concave mirror at 45 degrees

    I have a spherical concave mirror with focal length of 65cm, radius of curvature of 130cm. I hold the mirror close to the eye at approximate 45 degrees and I reflect an object below it as shown in the image. The distance between the object and the mirror is 90cm, that is more than the focal...
  23. G

    Mirror box with 1 candela of luminous intensity light source

    considering that a simple mirror may reflect 99.9% of the visible light
  24. P

    Combination of thin lens and concave mirror

    I created the following ray diagram to help me solve the problem: Then I applied the mirror equation 3 separate times. However, the final image distance I got is wrong. I'm wondering if I'm mistaken in taking the last object distance to be negative. However I only have one more try to get this...
  25. M

    Question about the operation of a current mirror

    Hi, I am in the process of trying to understand how a current mirror (shown in the diagram below) works. At a high level, I understand that we are trying to replicate the reference current (## V_{cc}/R_x ##) at the output. However, I am slightly confused as to how the current actually is...
  26. K

    ABCD matrix formalism for concave mirror

    Hello! I need to calculate the ABCD matrix for a thick concave mirror, in the situation in which the light comes from the plane side of the mirror, and it is the concave part that is coated (for reference, I have a Fabry Perot cavity with 2 concave mirrors, and I want to mode match the laser...
  27. Strange07

    Calculations for the movement of a light beam reflected by a mirror

    The only knowledge I have about such reflection questions is theta=2theta. But I missed class when this was thought. Please I need help and guide
  28. QuarkDecay

    Magnetic Mirror and particle trap

    Suppose we have two charged particles A and B released in the center of the Mirror (where the field is minimum). If A's velocity direction is parallel with the Magnetic field of the mirror and B's velocity is perpendicular with the field, then which one is going to get trapped, or escape, or...
  29. person123

    Optical Compact Device For Measuring Speed of Light

    Hi. This is an idea which I just happened to think of, and I was curious if it would be at all feasible. Here's a quick sketch I drew: The two curved mirrors should have a laser attached on one end and a video camera attached on the other. The laser would be tilted very slightly above...
  30. F

    Angle of reflection of a beam light on a moving mirror

    Before to open this topic, I found this there. It's quite similar, if not the same, but I'm a little confused, so I'm here. The situation is represented in this image. From optical geometry, ##\theta_{incident} = \theta_{reflected}## The four-momentum in ##S'## is the following one...
  31. DaveC426913

    Using a solar mirror to deflect a star

    I just finished Stephen Baxter's Manifold: Space. Great writer. Vast worlds he builds. In it, he has a project to deflect a star (a neutron star, to be exact) using a colossal mirror-sail placed on one side of the star. The idea is that the solar radiation bounces off the mirror and is...
  32. A

    Magnetic mirror concept -- electrons vs ions

    I am reading a book on fusion and just went over a paragraph of magnetic mirror confinement. What I want to understand is this. So all charged particles gyrate around magnetic field lines and if they have also a velocity parallel to the field they form helical paths. The gyroradius is...
  33. Imaxx

    I The Mirror Paradox: Exploring Special Relativity Theory

    Let's imagine that there are two people who has the same biological age. One is inside a spaceship, currently crossing a Quasar(A) in a constant velocity near the speed of light toward the Earth and the other is on Earth(B). In this situation, what will happen when A moves to the Earth and meets...
  34. A

    How far from the mirror should the light source be positioned?

    C= mirror center O = vertex I don't know if the design is right, if someone can show me the correct one. I also don't know how to proceed in geometry Solution: Lf / ( L - f( 1 + d/D))
  35. Frigus

    What is the logic behind the mirror symmetry method of solving circuits?

    I recently encountered mirror symmetry method of solving circuits and by it solving circuits became very easy but problem I am facing with it is that I can't figure out logic behind it. For example if we try to simplify this circuit Then we say that if ##I## current flows from Point A to C then...
  36. S

    Understanding Reflection of Light on a Concave Mirror

    My Basic Question is- Why can we see our inverted and real image inside a concave mirror when the image is formed in front of it and not behind? If you say that our eyes tries to image the real image formed by mirror on the mirror itself then- Imagine a situation where we have a concave mirror...
  37. A

    Magnetic mirror: pentagon or hexagon toroid?

    I know that the problem of magnetic mirrors is that they leak out the tight ends of the mirror, on the other hand the main problem of toroids is that magnetic field line curvature creates a better confinement on the inner diameter and lesser on the outer diameter so needs a strong plasma current...
  38. S

    Correct statement about a concave mirror

    Option (a) is wrong because if the person is standing at the focal point of the mirror, no image will be produced Option (b) is wrong because concave mirror can produce magnified image Option (c) is wrong because concave mirror can produce upright image Option (d) is wrong because sharp image...
  39. E

    Drop in intensity when light is focused to a point (telescope mirror)

    The parabolic mirror pictured below is such that all incident rays, neglecting diffraction, are reflected towards a focus. A question states that the light cannot be focused to a point precisely, since there exists a circular diffraction pattern in the focal plane. The following diagram is...
  40. CptXray

    Calculating Resonator Stability with Lens & Mirror

    I guess the resonator will be stable when both focal lengths of lens and curved mirror meet. The curved mirror is fixed and it's focal length: $$f_{curved} = \frac{R_{2}}{2} = 50 \, mm.$$ Then the d should be: $$d=f_{lens}+f_{curved} = 100 \, mm.$$ I think that's also the distance for which the...
  41. R

    How Can the Lorentz Force Be Used to Solve the Magnetic Mirror Problem?

    a) I know the invariants are $\mu = \frac{0.5*m*v_{perp}^2{B} $ and $J = v_{parallel} x b) I used the invariance of $\mu$ to get the following equation: $$ v_{perp}^2 = v_{perp,0}^2(1+\alpha(t)^2 z^2) $$ I am thinking of using the Lorentz force to get $v_z$, but I'm not so clear on how to go...
  42. Negatratoron

    Can an object be halfway between focal point and diverging mirror?

    A physics question from Principles of Physics by Mazur in the chapter on Optics is asking me to "repeat Problem 92 for a diverging mirror", and one of the questions in Problem 92 (which is about a converging mirror) is to find the image distance of an object halfway between the focal point and...
  43. U

    Understanding the Math Behind A: Minimum Length of Plane Mirror

    15. What is the minimum length of a plane mirror in order for you to see a full view of yourself? A 1/2 your height B 1/4 your height C 3/4 your height D your full height Q Why is answer of A given is the correct one, I understand pictorially how it is, since visually if you were to draw a...
  44. G

    I Light Speed Mirror Reflection: Can You See Yourself?

    If you’re traveling at the speed of light TOWARDS a mirror, will you be able to see yourself?
  45. P

    Can a convex reflection be corrected using a concave mirror?

    If one took a photograph of a reflection from convex reflective surface. Could one use concave mirror to obtain the original undistorted image?
  46. D

    How we see image inside the concave mirror when object is beyond C?

    In concave mirror, when object is beyond C ( centre of curvature) our traditional Ray diagrams show a real and inverted image formed between C and F. But at the same time, if we look directly into the mirror and remove the screen, we see an inverted image which appears to be inside the mirror...
  47. Marilyn67

    A Scientists are searching for a mirror universe....

    Hello ! What do you think of this article ? https://www.nbcnews.com/mach/science/scientists-are-searching-mirror-universe-it-could-be-sitting-right-ncna1023206 The paper dates from 2017 : https://arxiv.org/abs/1710.00767 In my opinion, it is very speculative, but a mystery is not yet...
  48. Manasan3010

    Reflection of a photon by an atom

    I suppose the reason I am able to see myself in mirror and not in wood is the reflection off a mirror is specular whereas wood is diffuse. In reflective material(e.g: silver) when the photon hits the frontline atom, the atom's electrons absorbs the energy and release it back with tiny energy...
  49. K

    Noisy Chiller: Solutions to Reduce Vibrations

    Dear forum members, We have a water cooled chiller device (see its model in attached link) and we use it to cool a hot mirror element. Unfortunately the chiller is vibrating and the vibrations couple all the way to the mirror through a pair of rubber tubes (1cm in diameter, 2m in length) and a...
  50. haushofer

    I How a mirror works: condensed matter explanation

    Dear all, in the context of my teaching I was wondering what exactly the explanation is of how a mirror works at the atomic level. Apparently, the fact that reflecting materials are often also good conductors and hence big energy bands helps reflecting the photons. Does someone know a nice set...