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. I

    Mirror Size & Height: Solving the Puzzle

    There is a woman who is 1,75m tall standing in front of a mirror. Her eyes are to be 10cm below the top of her head. I have to find out how small the mirror can be so that she can still see her entire body in it and how high it has to be hanging on top of the floor. Now I think I can solve it...
  2. R

    Find Focal Length of Mirror with 9.5 Magnification, 14mm from Object

    A mirror is required with magnification 9.5 when an object is 14mm from the mirror What is the focal length My attempt: M=v/u 9.5=v/14 v=133 1/f = (1/v)+(1/u) 1/f=(1/133)+(1/14) f=12.67 Since no object is magnified when the created image is outside of 2f this answer can't be...
  3. G

    How Does Magnification Change When Switching from Convex to Concave Mirror?

    A spherical mirror is polished on both sides. When used as a convex mirror, the magnification is +1/4. What is the magnification when used as a concave mirror, the object remaining the same distance from the mirror? I started with: mconvex = 1/4 mconcave = ? doconvex = doconcave...
  4. G

    Ray Diagram for Concave Mirror: Image Position & Height

    A 1.0 cm high object is situated 11.0 cm in front of a concave mirror that has a radius of curvature of 8.00 cm. Using a ray diagram drawn to scale (the mirror must be drawn to scale): (a) measure the location of the image: 6cm (infront of the mirror) (b) measure the...
  5. P

    Stargazing Check the profile of a telescope mirror

    Hi all, I know some men, who are amater astronomers. They made themseves reflective telescopes which can see the crescent Venus and many others in the sky. They say they make the mirrors parapolic shape although the depth of the mirror is very thin (about 1 - 2 mm). The diameters are often...
  6. R

    Will A Temperature Change Caused by Fire Line Crack Mirror?

    Hello, We have an installation in which we will be placing a 1/4" thick mirror which spans 7ft across and 5ft in height directly next to a "line of fire" (a gas pipe with holes which will have a flame approximately 6" in height). Our concern is that when the line of fire is turned on in...
  7. S

    Can anyone explain the unusual energy losses in my UV-laser mirror setup?

    I have a problem with which I would appreciate any help that is offered: I have a 266nm laser (frequency quadrupled 1064nm Nd:YAG), and the energy losses along the route are a little strange. The beam is reflected by two UV mirrors; however, the first mirror loses ~7% of the in-going energy...
  8. J

    Stargazing Liquid Mirror Telescope: How to create a parabolic shape

    I recently read about a proposed liquid mirror telescope to be constructed on the moon. My question is one of mechanics, hence this not being in the astronomy section. My question is regarding the shape of the surface of a rotating liquid. The design will have a dish containing a thin layer...
  9. M

    Size of image in a mirror problem

    1. When we talk about flat mirrors, it says that the size of image appears in the mirror is the same as of the object. Is the long rectangular mirror at home that is hang on the bedroom door to see how you look like when you dress up a flat mirror? If so, then when we approach the mirror, our...
  10. daniel_i_l

    Mirror Sunglasses: How Do They Work?

    How do mirror sunglasses work? I used to think that they worked like "one way mirrors" but those are just half silvered glass - meaning that if you are standing in a bright room looking through it into a dark one you'll see your reflection but if you look from a dark room into a light room you...
  11. P

    Base 2 odd numbers and their mirror image values

    Check this out: In base 2 take all (or the first several hundred thousand) the odd numbers and figure out the mirror image of the bit string for each number. Ex: mirror of 11111 is 11111 mirror of 1011101 is 1011101 mirror of 100000001111 is 111100000001 You can't really mirror an even number...
  12. L

    Apparent distance of object in planar mirror

    Tanya is sitting in an optometrist’s chair, facing a mirror that is 2.25 m from her eyes. It the eye chart she is looking at is hanging a wall behind her head, 1.75 m behind her eyes. How far from her eyes does the chart appear to be? Would the answer be 4 m? (2.25 m +1.75 m)... I'm...
  13. Alpha Russ Omega

    Reflecting glass and a convex mirror.

    Hello! I'm stuck on this problem... A thin flat plate of partially reflecting glass is a distance (b) from a convex mirror. A point source of light (S) is placed a distance (a) in front of the plate so that its image in the partially reflecting plate coincides with its image in the mirror...
  14. T

    What is a Magnetic Mirror and How is it Used in Various Fields?

    Hi guyz, Can anyone tell me what is the difinition of the concept "Magnetic Mirror" and give me enough information about it with examples? Thanks :)
  15. C

    Focusing light using a pyramidal mirror setup

    Hi, I was wondering if it would be possible to focus light down to a small point using the following method: Construct a pyramid from four identical triangular mirrors (three would also work), with the mirrored side facing inwards of course. Do not put a base on the pyramid, but instead use...
  16. H

    Mirror on the Wall: Light & Reflections

    If two planes of mirrors (infinite in all directions) were facing each other with nothing in between what would they reflect? How does light come into play in this?
  17. A

    Is there an easy way to remember the signs used for the mirror equation?

    Is there an easy way to remember the signs used for the mirror equation? For lenses? How does one keep the signs separate with talking about mirrors and lenses? I find it confusing... Please help, thanks!
  18. S

    How Does the Angle of Approach Affect the Speed of a Mirror Image?

    Homework Statement 1. Dubbie is moving directly along a normal line toward a plain mirror at a speed of 3.5 m/s, what is the speed of the image relative to Dubbie? 2. What is the speed of the image, relative to Dubbie, if Dubbie walk away from the mirror surface at 3.5 m/s at an angle of 300...
  19. B

    Discover the Focal Length of a Convex Mirror Using Object and Image Distance

    Convex mirror. PLEASE HELP! Homework Statement An object 30 cm tall is placed 20 cm in front of a convex mirror. If the height of the image is +10 cm, find the focal length of the mirror. Homework Equations The Attempt at a Solution I know to use 1/f = -(Image distance from V)...
  20. P

    Polished surface of metal as a mirror

    Hi everybody I am not so sure if this question is suitable to be in this box, but I hope it is. I know that all metals are opaque because they have lots of free electrons which absorb the energy of photons. But a polished surface of metal reflexes light other than absorbs it, especially...
  21. M

    Optimizing Rear-View Mirror Dimensions for Full Rear Window Visibility

    Homework Statement The rear window in a car is approximately a rectangle, 1.3 m wide and 0.30 m high. The inside rear-view mirror is 0.61 m from the driver's eyes, and 1.37 m from the rear window. What are the minimum dimensions for the rear-view mirror if the driver is to be able to see the...
  22. D

    At what distance is the object from the mirror?

    Homework Statement An object is placed in front of a convex mirror with a 65 cm radius of curvature. A virtual image half the size of the object is formed. At what distance is the object from the mirror? Homework Equations 1/p + 1/q = 1/f The Attempt at a Solution I have...
  23. M

    Settle my dispute- Can you see more of yourself in a mirror?

    When standing in front of my bathroom mirror (on the medicine cabinet above sink), I start to walk backwards. Will I be able to see more (or less) of my body in the mirror as I walk away from the mirror? Why? (For example, if I cannot see below me knees or above my eyebrows, will that...
  24. C

    Flash of a laser moves a mirror hanging on a rope

    Hallo to all members, this is my first post. Homework Statement A short Laser flush with the Energy E = 1J hits a ideally reflecting mirror, with mass m_m = 2 * 10^(-5) kg . The light has a wave length of 696 nm. The mirror is hanging on a rope with the length l = 0,1m. Homework Equations...
  25. R

    Find distance of image from the mirror

    Homework Statement The image formed by a convex mirror is only one third the size of the object. Focal length=12cm. Find distance of image from the mirror. Please provide me with the equation of this problem. Please!
  26. R

    Understanding Mirror Reflections: Solving for the Distance of a Third Reflection

    Homework Statement The reflecting surfaces of two parallel mirrors are facing each other. They are placed 10cm apart. A light source is placed in middle of the two mirrors. Calculate the distance of the 3rd reflection from the original point source in both the mirrors. Please tell me how...
  27. M

    Focus moonlight wth a mirror system

    Well, I'm new in town and I have a serious problem. Read the story and then tell me if its possible: In a open spot of a forest, a kid sees a sparkle from a 150 meters Manson's window. The house is located 5 meters above the forest floor level and the open spot 1-2 meters from the floor...
  28. B

    Capturing Light with a Theoretical Mirror Sphere: Observable? Possible?

    What would happen if: I had a sphere produced from a theoretical perfectly reflective one-way-mirror(reflective on the inside) and a shone a light into it? Would the light accumulate inside the sphere for a noticeable period of time? Would it be observable? Could light be captured this way...
  29. T

    Magnification of object in the mirror

    An object is moved along the central axis of a spherical mirror while the lateral magnification m of it is measured. Figure 34-32 gives m versus object distance p for a range of p. What is the magnification of the object when the object is 36 cm from the mirror? I understand that m=-i/p but...
  30. N

    Radius of Curvature of Convex Mirror: -17.39 cm

    A real object is placed at the zero end of a meterstick. A large concave mirror at the 100 cm end of the meterstuck forms an image of the object at the 82.4 cm position. A small convex mirror placed at the 20 cm pisition form a final image at the 6.3 cm point. What is the radius of curvature of...
  31. K

    What is the correct formula for calculating focal length in convex mirrors?

    I'm studying for a test that is going to cover mirrors and lenses. I was under the impression that the focal length for any concave or convex mirror was half the radius of curvature: f=r/2 but one of the questions in my book involving a convex mirror uses a different value for f, according...
  32. P

    Proving the Reflection of Light Ray from Parabolic Mirror on x-Axis

    I'm hopelessly stuck on this question. Any help will be greatly appreciated. Prove that if we have a parabolic mirror with focus at F and axis of symmetry the x-axis, then a light ray emmited from F will be reflected parallel to the x-axis. To prove this consider the parabola y^2=4px (where...
  33. J

    Concave mirror and virtual image

    we used a concave mirror and a candle for an experiment when the candle wa placed between the vertex and the focus of the mirror (f=12.7cm) a virtual image appeared behind the mirror. We measure the image distance approximately by pointing a finger towards where the image might be and got...
  34. J

    Experimenting with a Concave Mirror and a Candle

    we used a concave mirror and a candle for an experiment when the candle wa placed between the vertex and the focus of the mirror (f=12.7cm) a virtual image appeared behind the mirror. We measure the image distance approximately by pointing a finger towards where the image might be and got...
  35. J

    Why Did an Image Form at the Focal Point in Our Concave Mirror Experiment?

    We did an experiment with a concave mirror Concave mirror was placed on optics bench and a candle was placed at designated spots. A screen was used to see where the image was projected. But a strange thing happened. When the object was placed at the focal point, image was projected on the...
  36. C

    Where is the principle focus of a plain mirror?

    where is the principle focus of a plain mirror?
  37. J

    Calculating Force of Light on a Mirror

    "A 4.5W flashlight with a wavelength of 550nm is shined on a perfect mirror that reflects all the light completely. a) How many photon emanate from the flashlight? b) What force is exerted on the mirror by the beam of light?" A is easy, 1.25x10^19 photon/sec. My first attempt tried to...
  38. P

    How and why does a mirror reflect light?

    A fundalmental, atomic but also basic (2nd year Uni level maths and physics or less) explanation would be good.
  39. X

    Trouble with mirror equations, .

    heres the problem: a dentist wants a small mirror that, when 2.20cm from a tooth, will produce a 4.5x upright image. what kind of mirror must be used and what must its radius of curvature be? so i did the following calculations with the mirror equations i learned: m=4.5 equation to get...
  40. D

    Uncover the Mystery: Why You See a Real Image in a Concave Mirror

    Hi Why is that you can see a REAL image in a concave mirror when you are looking into the mirror?[/FONT] i tried searching the answer on the net but could not find the answer. please help thanx in advance.
  41. B

    Measuring refractive index of liquid using lens and mirror

    hi i've got to do measure hte refractive index of a liquid with mirror and lens first of all how can i measure hte refractive index of air in this way? i don't get how i can do this, please explain :| and then for the liquid, I've been told to put the liquid over the mirror and then the...
  42. J

    Help with concave mirror question

    here's the question asked: Find the two locations where an object can be placed in front of a concave mirror with a radius of curvature of 36 cm such that its image is five times its size. In each of these cases, state whether the image is real or virtual, upright or inverted. 1. i have...
  43. Amith2006

    Image formed by a convex mirror

    Sir, I am posting these questions for the 3rd time as you didn't respond. Please respond. 1)A convergent beam of light is incident on a convex mirror of radius of curvature 60 cm as shown in figure. What is the nature and position of the image formed by it? I solved it in the following way...
  44. Amith2006

    Nature of image formed by a plane mirror

    Sir, 1) A beam of light incident on a plane mirror forms a real image on reflection. It is said that the incident beam in that case is convergent. Is it true? I think it is due to the fact that a plane mirror normally forms virtual images of real object. In order that a real image be...
  45. Amith2006

    Image formed by a convex mirror

    Sir, 1) A man 2 meters tall stands 5 meters in front of a large vertical plane mirror. What is the angle subtended by his image in the mirror at his eye? I solved it in the following way: Let AB represent the man and CE represent the mirror mounted on the wall.Here I am assuming that the...
  46. T

    Radius of Curvature of a 10cm Concave Mirror

    A concave mirror has a focal length of 10 cm. what is its radius of curvature?:eek: i have absolutely no idea how to solve this, please help:cry:, any advice is greatly appreciated:smile:
  47. N

    How Does Light Reflect from a Mirror to Create a Bright Streak on the Floor?

    I have a question dealing with light and a mirror. q: A dressing mirror on a closet door is 2.0 m tall. The bottom is 0.5 m above the floor. A bare light bulb is attached to the ceiling, which is 3.0 m above the floor. The light bulb is 1 m from the closet door. The light from the bulb shines...
  48. T

    Viewing you full length in a mirror

    Hey guys, I've got a quick question if you don't mind. I understand that in order to view your full length in a mirror, that only a half-length mirror is needed; however, I'm wondering if this is true to just only see your face (if it was held up in front of you). So if my face is 15 inches...
  49. J

    X-ray Mirror to be used by telescope

    Hey all!, I'm working on a project in which I have to design the shape of a mirror to focus X-rays. This is basically what I've done so far so far. I've found that if you use a parabola mirror it will focus parallal rays, but not off-axis ones. If you then add a second mirror in the form of...
  50. Doc Brown

    Question about reflecting sunlight off a mirror

    First off, I apologise for this basic (and rather random) question. I am not educated in this area, in fact I have no education in physics whatsoever, but an idea for an invention came to me over the weekend and whether it is feasible or not depends on the answer to this question. I have enjoyed...
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