Mirror Definition and 654 Threads

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. Z

    Mirror Equations: Derivation of Newtonian Form

    Hallo, First time I've experienced a real problem rearding equations in physics, so: As conclusions to the lab on focal points and and center of curvatures (which will be explained at a later date), we were given the following relationships: So = Do - f Si = Di - f And, we were...
  2. M

    Did I assume too much in this problem? Stuck on some trig, simple mirror.

    Hello everyone. I was hinted by a member that I should use pythagoris and some trig to figure the length out. It all made sense but now I'm not getting the right answer and I'm wondering if its becuase I assumed the first triangle had a length of 3.10, because it said the bird is 3.10m from...
  3. M

    An image is magnified by 2.50, concave mirror confusion wee

    Hello everyone< i think I'm on the right track but now I'm stuck. Here is the problem: A concave shaving mirror has a radius of curvature of 37.0 cm. It is positioned so that the (upright) image of a man's face is 2.50 times the size of the face. How far is the mirror from the face? Here is my...
  4. M

    Troubleshooting Convex Mirror: Image Distance & Magnification

    Hello everyone, I seem to be getting all the mirrors right that where concave but now i have a convex one and it doesn't seem to be working when im' finding the image distance and magnification/properties. Here is the problem: Heres my work: both the i and the m where wrong, i also tried...
  5. M

    How Do You Calculate Image Distance in a Plane Mirror Setup?

    Hello everyone! We just had our first class today and it seemed to make sense but now the homework is confusing me on what is what. Here is the problem: You look through a camera toward an image of a hummingbird in a plane mirror. The camera is 4.30 m in front of the mirror. The bird is at...
  6. B

    How can a thin mirror show such vast depths?

    this is something that has confused me for quiet some time. the mirror is just a few millimeters thick. then how is it that we can use it to see depths of metres and kilometers. what is it that enables a mirror to show greater depth than its own
  7. C

    What is the object distance for a concave mirror?

    Hey eveyone, I have a concave mirror and an object x distance away from the mirror. I am wondering if anyone knows where you measure from in order to determine how far away the object is from the mirror. Is it from the object to the center of the concave mirror? Thanks, ccflyer
  8. N

    Do Mirrors in Quantum Experiments Act as Measurement Devices?

    Considering (again!) which way type of experiments (the interference type of set ups when a photon may go through two different routes and then one recombines the paths and checks for the presence of absence of interference (as used in quantum erasers, etc)). Usually, people say that if there...
  9. Mk

    I just looked at my hair in the mirror

    It was really shinny. Is shinny hair good? A take on this from the ladies would be good.
  10. A

    How Do Sign Conventions Affect Calculations in Spherical Mirrors?

    Hi, Doing an optics course I'm getting a bit confused about sign the conventions at time, can somebody check my answers here? A spherical concave mirror of radius, R= 100mm has a real object placed at an axial distance So from its vertex. Q1 Obtain the focal length of the mirror 1/ f =...
  11. I

    Explaining the Infinite Reflection of a Pencil in Mirror Photography

    I have a project in school in which I have to take a picture of a physics phenomenon that has to do with light and reflection. So I was thinking to use flat mirrors and put two of them in front of each other. How would I explain why the pencil I put in the middle is reflected infinitely and...
  12. C

    Finding height of image for a concave mirror

    Ok, there's something I just don't understand. I know that to find the height of an image (hi), you need to use the magnification equation m = -di/do = hi/ho. And for this question, the focal length (f), distance of object (do), and distance of image (di) are given. Now, if I want to find the...
  13. P

    What is the loss percentage of standard glass mirrors in multiple reflections?

    I have two mirrors at the same height on opposite walls facing each other in my bathroom. I took a laser pointer and put it in between the mirrors and directed the beam at one, such to where the reflected beam hit the other mirror, and back on the first and so on. Anyway, I noticed probably 16...
  14. P

    How Do You Determine Image Location and Type Using a Spherical Mirror Equation?

    If you place an object a distance so from a spherical mirror, how do you calculate the image location given that the image is right side up and magnified by two times? I know the equation but I always get confused about what signs to use for lenses vs. mirrors, etc. I know the magnification...
  15. C

    Determining the Minimum Length of a Plane Mirror to View a 5m Drawing

    a man is standing with his back facing a large drawing of 5m long, and his front facing a plane mirror.the mirror is placed at eye level, to enable him to see the image of the drawing.what is the minimum length of the plane mirror if he were to see the whole image of the drawing? 1)2m...
  16. P

    Shortest mirror that will work

    Shortest mirror that will work... 1. How long does a "full length" mirror have to be to allow you to see your whole body? What is the shortest mirror that will work? How should a mirror be positioned? :rolleyes:
  17. I

    Bat and mirror relativistic problem is my solution good ?

    So the bat is flying with velocity 172 m/s and he see himself in mirror which is parallel to the direction of fly. He can himself in the mirror because he send a sound signals with velocity 344 m/s. So now i have to count angel to the direction of motion. a) first in arrangement of air b) in...
  18. T

    Mirror Reflection: Left-Right Exchange Explained

    Why is it that a mirror reflection only exchange the notion of left-right but not up-down ? I mean if I were to stand in front of a mirror, my mirror image exchanges my left hand with the left, but not my head with my legs.
  19. H

    Gaining Comfort from a Second Mirror Image: Perspectives on Life

    Rather than going to a barber shop and paying $15 for a haircut every month I bought some clippers and cut my own hair. Last week I used them to cut my hair and wasn't sure how the trim on the neckline looked. I asked one person and they said it looked fine. I asked another and they said it...
  20. M

    How Do Double Concave Mirrors Create a Floating Image?

    I am trying to figure out how those double concave mirror set ups work to create an image above the mirror. Does anyone know what I am talking about? You have 2 [spherical] concave mirrors, both with the same radius of curvature (and thus the same focal length), one facing up, and the other...
  21. F

    Understanding Relativity: How a Mirror Reflects Your Image at Near-Light Speeds

    If you hold a mirror at arm's length and look at your reflection, what will happen as you begin to run and a speed close to that of light (v=.99c). Will you still be able to see yourself? Will your image look any different?
  22. J

    Mirror image reversal - why only l/r, not up/down

    what explains the fact that mirrors only reverse an image left to right, not up and down?
  23. H

    Mirror Image Problems in Electrodynamics

    What do the mirror image problems in electrodynamics exactly focus at? Are they only based on the uniquesness theorem ,which we study in Differential equations.!But i find their application to be limited since they can be applied to a surface which is grounded.! One more thing ,how does it...
  24. J

    Why doesn't a mirror reverse top to bottom?

    If a mirror reverses left to right, why doesn't it reverse top to bottom?
  25. E

    Half silvered mirror experiments

    Can I ask a stupid q? Using Wheeler's delayed choice experimental setup, one can vary the path length of one of the legs. This enables making all the photons end up at one detector and none at the other. Is this correct? If so, where did the uncertainty go? Can the interference pattern be...
  26. S

    Concave & Convex Mirrors: Real/Virtual Images Explained

    Why can concave mirrors produce a real or virtual image, but convex mirrors can produce only one virtual image?? As well, when an object is moved along the principal axis towards the vertex of a concave mirror, the image changes. Where exactly does this change occur and why? I know it has...
  27. S

    Scientists cover the mirror with a stratum that doesn't hold water

    I'm a high school student. I heard that scientists cover the mirror with a stratum that doesn't hold water. Thus when you get out of the shower, you can see your reflection into the mirror in a smooth way. I've been searching this structure. I want to indicate my ideas with composing...
  28. S

    What materials make the best mirrors?

    What is the difference between a mirror and a white surface?What I know is: 1. A mirror reflects light such that an image is formed. The angles of reflection and incidence are equal. It reflects all wavelengths of light. 2. A white surface reflects all visible wavelengths of light. It...
  29. N

    Virtual mirror on the road on hot days. Why is that?

    While in a car on a hot day, I notice that far ahead of me is a mirror-like surface on the road. I can see the reflections in that virtual mirror too. The mirror shifts with your moving forwards. Can anyone give a simple explanation? Thanks.
  30. M

    Running real fast while holding a mirror

    Hello if you're running and looking at your own imagine in a mirror you're holding in your hand, how would the image look like? what if you were running at .99c ? and why?
  31. C

    Calculating Rearview Mirror + Amusement Park Mirror Images

    I have 2 questions: What type and height of image would a rearview mirror produce of a car that was 1.3 m high and 15.0 m behind you, assuming the mirror's radius of curvature is 3.2 m? I don't know what equation to use to solve the problem. I think it might be: (1/object distance) +...
  32. S

    Cleaning a reflector mirror without scratching it

    Hi all. I have a very heavy 9" reflector but it is has spherical curve. It was made for a semiconductor projection aligner which was being scrapped and I saved the mirror from going into the trash bin. I saw an article in one of the rags about making a frame on the back of the mirror where...
  33. L

    Mirror Color: Do Mirrors Have a Color?

    the mirror only reflects light and produce image of other objects. so what's the color of a mirror actually?
  34. M

    Prevent Bathroom Mirror Fogging with Soap

    Whenever you take a shower the bathroom mirror fogs. I discovered if one rubs a thin layer of soap on the mirror, then gently rubs it in with a cloth, the mirror does not fog. I could not think of any other reason other than some chemical reason. Why does this happen?
  35. S

    What frequency of light is recorded by a detector attached to the moving mirror

    A stationary light source S wit ha natural frequency Fo is viewed in a mirror M by a stationary observer O. The mirror moves away from the observer wit ha velocty of Vrel << c a) what frequency of light is recorded by a detector attached to the moving mirror because Vrel << c classical may...
  36. K

    Solving Mirror Questions: Formula & Examples

    I have a few mirror questions. I missed class and didnt get the formulas to do these. If some one could help me out it would be appriciated. The formulas I have in my notes are 1/f = 1/do + 1/di and hi = (ho * di) / do. I don't think I have enough info to use these formulas and I am guessinf...
  37. J

    How Does Refraction Affect Image Location in a Bi-Radial Mirror?

    A piece of glas has an index of refraction of 1.5. The ends are hemispheres with radii 2 cm and 4 cm, and the distance that separates the centers of the hemispherical ends. A point object is located in air 1 cm from the left end of the glass. Find the location of the image of the object due...
  38. A

    Simple thinking problem - mirror refraction

    Suppose you want to take a photograph of yourself as you look at your image in a flat mirror 1.8 m away. For what distance should the camera lens be focused? You must be ½ the total distance away: since the angle of incidence is equal to the angle of reflection, the distance needed to get a...
  39. N

    Optimal Vertical Mirror Height for a 5'0'' Person: Calculating the Perfect Fit

    determine the minimum height of a vertical flat mirror in which a person 5'0'' in height can see his or her full image. I have absolutely no idea how to solve this type of problem... Since we don't know the distance between the object and the mirror, how in the world can we calculate the...
  40. K

    How can I solve these mirror problems without getting the wrong answer?

    This is driving me crazy I am ready to either bash my head through a window or kill something. I can't get any of these homework problems and I have no idea why... These are webassign problems so it tells me if its the wrong answer but naturally doesn't tell me what I'm doing wrong... so I am...
  41. D

    Why is it that in a mirror that my image is flipped

    i was wondering why is it that in a mirror that my image is fliped but not upside down, why is it in just one plane.
  42. M

    How Does a Mirror Reflect Light at the Atomic Level?

    Sure, everyone knows that the angle of incidence equals the angle of reflexion. My question is rather aimed at the atomic level. What is the interaction between electromagnetic radiation and matter? Why can a layer of metal (a mirror) reflect light? Does the interaction occur at the electron...
  43. S

    What is 'Mirror Gain' for a Robot Parabolic Mirror?

    Hi, I've asked someone to make me a parabolic mirror for a robot and they want to know the 'mirror gain' i would like. Does anybody know what 'mirror gain' is? thanks
  44. H

    Converging lens and Concave mirror

    A converging lens (convex) and a concave mirror, both of focal length 5.0 cm, are arranged with their axes in line. The lens and the mirror are 10.0 cm apart and a candle is placed 3 cm infront of the mirror. By using a ray diagram or some other metho, find the location of all the images...
  45. K

    How Do You Determine Object Location and Magnification in a Concave Mirror?

    Well, here is the problem: A girl has her 2-cm high eye 12 cm directly in front of a concave mascara mirror or focal length 18 cm. Where is the object located, and what is the magnification? I'm really lost on this one. EDIT: Sorry, I just realized this would be better suited for the...
  46. A

    Convex mirror, and you point a light at it horizontally

    If you have a convex mirror, and you point a light at it horizontally, does the light always reflect through the focal point? (the point halfway on the line connecting border and the center, parallel to the light's initial path) I remember learning this, but I think of a mirror in the shape...
  47. C

    Image Location for a Double Concave Mirror (-20 in Focal Length)

    if a double concave mirror with a focal length f = -20 inches is used , where does the image seem to be located , if the image is 30 feet away from the lens first i converted the 30ft to inches and got 360inches used formula 1/p + 1/q = 1/f .0028 + 1/q = -.05 1/q = -.053 q = -18.9...
  48. M

    So the sheet of paper should be placed 24 cm from the mirror.

    Mirror due Midnight! Problem 32. A concave spherical mirror can be used to project an image onto a sheet of paper, allowing the magnified image of an ulluminated real object to be accurately traced. If you have a concave mirror with a focal length of 16 cm, where would you place a sheet of...
  49. D

    Diverging Lens and Concave Mirror

    Can someone get me started on this, I know how to work a diverging lens and a concave mirror, just not together. The problem: A concave mirror with a radius of curvature of 20.0 cm is placed 25.0 cm from a diverging lens with a focal length of 16.7 cm. An object is placed midway between the...
  50. L

    Telescope mirror polishing simulator

    Greetings All, I am attempting to develop a software simulation of the dynamics involved in machine figuring concave parabolic telescope mirrors. As a member of the amateur telescope making community, we currently don't have any tools to do this other than the "trial and error" method...
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