What is Reflection: Definition and 953 Discussions

Reflection is the change in direction of a wavefront at an interface between two different media so that the wavefront returns into the medium from which it originated. Common examples include the reflection of light, sound and water waves. The law of reflection says that for specular reflection the angle at which the wave is incident on the surface equals the angle at which it is reflected. Mirrors exhibit specular reflection.
In acoustics, reflection causes echoes and is used in sonar. In geology, it is important in the study of seismic waves. Reflection is observed with surface waves in bodies of water. Reflection is observed with many types of electromagnetic wave, besides visible light. Reflection of VHF and higher frequencies is important for radio transmission and for radar. Even hard X-rays and gamma rays can be reflected at shallow angles with special "grazing" mirrors.

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  1. S

    Why Does Water Make a Perfect Mirror?

    First off, let me apologize if this is in the wrong section, but I was not entirely sure what branch the answer would fall under. Okay, my question is this (and its probably pretty obvious): If water is clear, what makes it an almost perfect mirror when you look across a still lake? My...
  2. C

    Total internal reflection with Sound?

    In Diamonds, light that enters gets trapped within due to total internal reflection, defined as: Total internal reflection is an optical phenomenon that occurs when a ray of light strikes a medium boundary at an angle larger than the critical angle with respect to the normal to the surface...
  3. G

    How Do Refraction and Reflection Differ in Optics and Sound Waves?

    Could some explain the difference in refraction and reflection in optics and sound waves?
  4. G

    Total internal reflection, underwater light

    [Solved] Total internal reflection, underwater light? Homework Statement A point source of light is at the bottom of a koi pond, at a depth of 0.525 meters. What is the radius of the circle of light formed on the water's surface? Take the index of refraction of water to be 1.33. Hint: Some of...
  5. D

    Minimizing Reflection of Light: Coating Glass with n = 1.44

    A material with an index of refraction of 1.44 is used to coat glass. The index of refraction of glass is 1.5. What is the minimum thickness of the coating that will minimize the reflection of light with a wavelength of 4680 A? Answer in units of µm. I know that the thickness for this is t =...
  6. C

    Angle of Incidence for Internal Reflection

    Homework Statement In the figure shown below, a light ray enters a glass slab (with index of refraction nglass = 1.65 ) at point A and then undergoes total internal reflection at point B. The medium that surrounds the glass slab is a liquid whose index of refraction, nliquid =...
  7. H

    Calculating Bouncing Velocity from Tangent Angle in 2D Collision

    Hello there, Let me start by saying this question is going to make me look somewhat ridiculous considering the complexity of most other questions floating around here, but I'm not a maths or physics student and never have been; rather I'm a graphic designer with a basic query in relation to a...
  8. S

    Quantum particle reflection from a potential drop

    Homework Statement A quantum mechanical particle with mass m and energy E approaches a potential drop from the -x region, where the potential is described by: V(x)=\left\{\stackrel{0 textrm{if} x\leq 0}{-V_0 textrm{if} x> 0}. What is the probability it will be reflected by the potential...
  9. M

    Angles of Reflection of Light

    (SOLVED) Calculator Entry ErrorAngles of Reflection of Light A ray of light strikes a flat 2.00 cm thick block of fused quartz (n = 1.458) at an angle of θ = 27.0° with the normal (Fig. P22.18). Trace the light beam through the fused quartz and find the angles of incidence and refraction at...
  10. S

    Feynman's QED Lectures: Questions about partial reflection

    In Feynman's lectures he describes partial reflection as occurring because the "little arrows" cancel out when the glass is certain thickness. I realize that there isn't an actual model of how QED works but what exactly does he mean by "cancel out"? Also when do you shrink and turn the little...
  11. P

    Angle of reflection equation?

    I have an assignment to due and it asks for the angle of reflection, but I don't know how to get it. This is the question: "A beam of light is directed on the flat surface of a block of fused quartz (n=1.92). Part of the beam is refracted with an angle of refraction of 30°. What is the angle...
  12. C

    Mirror Reflection: Seeing Double?

    Hello all, I have a quick question. If i put two identical mirrors right next to each other on the same surface at the same level and stand in the middle of it will i see two of me or will it act like looking myself if that mirror was one single piece. Thanks!
  13. P

    Calculate qout: Angle of Reflection in Two Mirrors

    Light is reflected by two flat mirrors that have an angle q = 114 degrees between them. If the initial ray makes an angle qin = 66 degress with respect to the normal, what is qout? http://img95.imageshack.us/img95/4791/mirrorxz9.th.png I know that the angle of incidence is equal to the...
  14. G

    Two total internal reflection examples

    Homework Statement -Behind a glass container with water, there is a candle. The container is paralelopiped - shaped. What is the image that the viewer is going to see, if the eye is set like so, that he watches the candle with an angle greater than the angle of total reflection? -Hold a...
  15. F

    Reflection of Photons on Prisms: Directional Force?

    Do photons reflected off prisms exert directional force however small as they are reflected off the hypotenuse side of a right triangle shaped prism?
  16. I

    Solving Wave Equations with a Wall - Reflection and Amplitude

    Homework Statement We have waves propagating in the air. First part asks for a traveling wave solution in the x direction , given a wave length 2pi and amplitude 3m. I have obtained u(x,t) = 3 cos ( x - 345t). The question then asks what happens if a wall is placed at x=0, what is the form of...
  17. G

    What is the Matrix of Reflection in Euclidean Space?

    Homework Statement V is a three-dimensional euclidean space and v1,v2,v3 is a orthonormal base of that space. Calculate the Matrix of the reflection over the subspace spanned by v1+v2 and v1+2*v2+3*v3 . Homework Equations The Attempt at a Solution To determine the matrix I...
  18. B

    Refraction and Total Internal Reflection

    http://img210.imageshack.us/img210/6094/questionuz8.png i) What is the angle of refraction of the ray RS after it strikes the glass prism of refractive index=1.5? ii) If the critical angle is 41.8 degrees, deduce whether the ray will suffer total internal reflection. 2. Homework Equations ...
  19. F

    Light Reflection between Mirrors: Facts & Myths

    Why are we not able to capture and store light between two mirrors? I'm going to take a guess at the answer but I'd like to hear from someone who knows for sure... I'm wondering if you actually can for a small amount of time, but the inefficiencies of an imperfect mirror cause some light to be...
  20. M

    Phase Change at reflection:

    Homework Statement Part of a longer question, what is the phase change, if any for a system of three substances of different n where there is surface reflection between n1 and n_f which is meant to constructively interfere with another surface reflection between n_f and n3.where n1 < n_f >...
  21. B

    Total Internal Reflection Question

    I have written in my notes the following: "Total internal reflection will have reflecting ray only, same as incident (60 degrees)." I understand everything but the 60 degrees part. If there is total internal reflection, will the angle of reflection and the angle of incident both always be...
  22. J

    Internal Reflection Problem

    [SOLVED] Internal Reflection Problem Homework Statement (please check attachment for figure) ni = 1 nr = 1.48 theta_I = 50 degrees l = 3.1 mm w = 42 cm Find N (Number of reflections before laser beam finally emerges). Homework Equations Snell's Law: ni sin theta_I = nr sin theta_r The...
  23. B

    Reflection and refraction of light problem

    Homework Statement 3. Assume the slab is perfectly rectangular and has width W. (a) Calculate the distance (L) the light travels INSIDE the block as a function of W and the angle t1. (b) From the right-angled triangle with vertices IPE calculate the lateral displacement x in terms of...
  24. C

    Calculating Reflection Coefficient for a Potential Well

    Homework Statement A potential well with V(x)=0 for x<0 and V(x) = Vo for x>0. The particle has energy E greater than Vo and is incident from the left side. Calculate the reflection coefficient. Homework Equations Relfection coefficient is given by R= (B*B)/(A*A) The Attempt at a...
  25. I

    How does the reflection formula for vectors work?

    Could someone explain how the reflection formula comes about? R_a v = v - 2a(va)/ (aa) , where v and a are vectors and v is relected along the axis orthogonal to a thanks
  26. K

    Question about light reflection

    Homework Statement A diver shines a flashlight upward from beneath the water at a 23.0° angle to the vertical. At what angle does the light leave the water? Homework Equations I thought that i could use snell's law here...but i don't know what to do afterwards... The Attempt at a...
  27. D

    [thin films] (Macleod's) phase-shift upon reflection

    Folks, I'm reading the 3rd edition of Thin Film Optical Filters by Macleod, and I've derived his expression for phase shift upon reflection (page 45). Finally, it lead me to a question. Any help is highly appreciated! \rm E_i + E_r = E_t \qquad (1) \rm H_i - H_r = H_t \qquad (2)...
  28. M

    Solve Magnifying Glass Image Distance w/ Focal Length 17cm +2.00 Mag

    Homework Statement A magnifying glass has a converging lens of focal length 17.0 cm. At what distance from a nickel should you hold this lens to get an image with a magnification of +2.00? Homework Equations 1/F=(1/Dobject)+(1/Dimage) M=-Dimage/Dobject The Attempt at a Solution...
  29. S

    Total internal reflection (T.I.R.)

    Why is it that T.I.R. only occurs when a light is traveling from a denser to a rarer medium? Intuition suggests that this should happen when going from a rarer to a denser medium. Care to get into some mathematics? Also, can the interface between 2 media be designed so that there is 100%...
  30. J

    Reflection Diffraction Gratings

    My lecturer has given me this formula for reflective diffraction m landa = d (cos a - cos b) where m is order # landa is wavelength d is slit seperation a is angle of inicdence b is angle of reflection The problem I have is I wasn't given any justification of this and have...
  31. L

    Distance of Image from Object in Plane Mirror - Caution with Convex Mirrors

    Q#1. Homework Statement [/b] an object and an observer are located 2meter in front of a plane mirror, If the observer is 3meter from the object, find the distance between the observer and the location of the object's image. Q#2. the image produced by a convex mirror is always closer to the...
  32. T

    Reflection of light - the physics of a mirror

    How does reflecting of a light works? In physics people keep talking about mirrors in lasers and optics, etc. but how does mirror works at sub-atomic level? Does the light wave simply excite the electron which then sends identical wave in opposite direction? Or does it simply bumps off a...
  33. M

    Problem 23.11 Light reflection

    Homework Statement It is 171 cm from your eyes to your toes. You're standing 210 cm in front of a tall mirror. How far is it from your eyes to the image of your toes? Homework Equations ? The Attempt at a Solution The answer which I got from the back of the book is 433cm. I have the...
  34. M

    The Phase Change of Pi at Atomic Level: Exploring Reflection Phenomena.

    Please explain the phenomena of reflection at atomic level ? We know that on reflection a phase change of pi occurs i/e phase difference b/w reflected & incident beam is pi , explain this phase change of pi at atomic level ? What is actually meant by phase change atomic level ?
  35. S

    Reflection coefficient at a copper boundary

    Homework Statement Calculate the reflection coefficient of copper for radio waves at frequency 50Ghz and yellow light (wavelength = 0.6 micrometers) Homework Equations Reflection coefficient: R = E(r)^2/E(I)^2 = (1-n/1+n)^2 Where E(r) is the electric intensity of the reflected wave...
  36. J

    Which Liquid Requires More Volume to Conceal a Coin: Oil or Water?

    Question on total reflection...if you were to conceal a coin, by putting it under a beaker whose lid is covered with foil, and you slowly add a liquid until the coin seemingly disappears, which would require a greater volume? oil or water?
  37. P

    Why Does a Spherical Mirror Invert the Image of a Thin Object Along Its Axis?

    Homework Statement A short thin object (like a short length of wire) of length L is placed along the axis of a spherical mirror (perpendicular to the glass surface). Show that its image has length L' = (m^2)*L so the longitudinal magnification is equal to -m^2 where m is the normal...
  38. M

    Investigating the Effects of Pregnancy Gel on Ultrasound Reflection

    (Not Spam :tongue:) I did a bit of reading today on partial reflection when using ultrasound. I was reading about a pregnancy gel that is applied to the womans stomach when detecting a baby. To put it briefly, if the ultrasound transmitter is held away from the body a lot of energy is...
  39. M

    What is the Law of Reflection for Waves on Solid Surfaces?

    I am having trouble understanding this idea, I will quote what I have read and then post an image. This is not a homework question if anyone asks, it is an extension of what I am doing at school, but I would like to do some work through my week off. :tongue: "Waves that are incident on solid...
  40. ZapperZ

    FINAL VOTE Photo Contest - A Moment Of Reflection

    This promises to be a very difficult final vote since all the pictures that made it this far are outstanding. Please vote for the picture that best represents our theme, which is a reflection of an image. 1. Chi Meson 2. larkspur 3. fi...
  41. ZapperZ

    VOTE Photo Contest - A Moment Of Reflection (Group 2/2)

    This is the second group in this contest. You have one vote. Please vote for the picture that best represents our theme. 1. Janus http://home.earthlink.net/~parvey/sitebuildercontent/sitebuilderpictures/reflect.jpg 2. Mech_Engineer 3. fi...
  42. ZapperZ

    VOTE Photo Contest - A Moment Of Reflection (Group 1/2)

    This could be a brutal voting process. There are many outstanding pictures in this contest. The pictures are in 2 different voting threads, so you have 1 vote for each group. Please vote for the picture that best represents our theme, which is to depict a reflection. 1. Chi Meson 2...
  43. P

    What happens with the atoms, while reflection of light?

    what happens with the atoms, while there is reflection of light? What happens with the electrons or protons, are they reflecting the light and how?
  44. ZapperZ

    PF PHOTO CONTEST - A Moment Of Reflection (1/19-1/25)

    A Moment Of Reflection Our theme this week is on pictures that includes images that have been reflected. The images can be reflected off mirrors, water, smooth surfaces, etc. However, please note that the pictures must show clearly that what we're seeing is a reflection, especially when it is...
  45. A

    Draw Incidence Angle of reflection

    Homework Statement Look at the diagram. Draw the wavefronts as they would appear after the reflection. Draw and identify the following things on the diagram. Incident ray Normal Reflected ray Angle of Incidence Angle of reflection Homework Equations n/a The Attempt at a...
  46. 6

    Does the Doppler Effect Double the Color Shift of a Moving Light Source?

    I am having a friendly argument with a friend. If a light source was moving towards a colored object at high speeds in a completely dark area, would the color shift due to the Doppler effect be doubled? Possible theories are no (which we agree is wrong) Yes (which may be right) Or simply...
  47. H

    Can Covering Earth with Aluminum Foil Help Reduce Global Warming?

    If one is trying to reduce Earth mean temperature, why not cover it with aluminum foil? :D
  48. M

    Total Internal reflection question

    [b]1. A white light source is below the lower surface of a piece of optical-quality glass. The glass has an index of refraction of 1.520 for red light and 1.538 for violet. If you were able to move your eye at any angle relative to the perpendicular to the glass, calculate A) Which color...
  49. P

    Find Distance of Lamp from Mirror to See its Reflection

    Question: At the bottom of a glas bath lies a mirror covered by 20cm of water.In the air,30 cm above the water there hangs a lamp.Find the distance from the mirror at which an observer looking into the water will see the image of the lamp in the mirror Relevant Formula: apparent shift...
  50. M

    How to Calculate the Initial Angle of Incidence in a Mirrored Maze?

    Homework Statement In an amusement park maze with all the walls covered with mirrors, Pilar sees Hernando's reflection from a series of three mirrors. If the reflected angle from mirror 3 is 52° for the mirror arrangement shown in the figure, in which = 12°, what is the angle of incidence on...
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