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. E

    Specular reflection from moving mirrors

    Question: Does the law of specular reflection (angle in = angle out) for obliquely incident light rays still hold if the mirror is translating in a direction parallel to its normal direction? If not, what different effects attend said translation if a) the motion is toward or away from...
  2. A

    Reflection of color in opaque and transparent materials

    Hi, The textbook I am using does not clearly explain why certain objects reflect certain frequencies of color. If the frequency of light matches the frequency of the opaque object it is shined upon, will it be absorbed or reflected? I'm thinking that it may be absorbed for the same reason...
  3. D

    Colours of objects produced by light due to reflection & absorption

    Colours of objects produced by light due to reflection & absorption! Hi fellow members! We know that colours of our surrounding things is due to the absorption & reflection of particular wavelength of light. But we also see same colours of objects in bulb light aur tube light. Do they also...
  4. S

    Projection and Reflection of Vector WRT plane

    Homework Statement Given a plane \Pi with normal n=i-2j+k and a vector v=3i+4j-2k calculate the projection of v onto \Pi and the reflection of v with respect to \Pi. The Attempt at a Solution I need to check that I'm doing this is right. I think I need v - (v \cdot n)n =...
  5. S

    Reflection of EM plane wave from a moving object

    A plane wave normally incident onto a perfectly conductive surface moving in the normal direction with constant velocity comparable to the speed of light. How do I solve such problem? If I treat the conductor as static, and the source of plane wave as a moving source, do I only need to consider...
  6. K

    Finding the stable line of a Glide reflection

    1. For the following matrix, determine whether it is a translation, rotation, mirror reflection, or a glide reflection and find its fixed points and stable lines. Homework Equations Given the matrix D= .8, .6, 2 .6, -.8, 1 0, 0, 1 The Attempt at a Solution First I got...
  7. S

    Is it Total internal reflection, or something else?

    Is this process known as "total internal reflection"? Or is it called something else? What is the name of this process that causes the entire material to light up even though the light is applied only to one side? Take a look at the photos so you can see what I am asking about. Notice how...
  8. J

    How Does Reflection Coefficient Change in Lossy vs Lossless Media?

    I've been reading over Balanis' Advanced Engineering Electromagnetics in an effort to teach myself a bit about Electromagnetism. I've stumbled across a question (not one in the book) that I can't seem to wrap my head around. If there's a lossy dielectric or medium, how does the reflection...
  9. E

    Amplitude reflection coefficient for high to low refractive index

    For a wave traveling from a medium with refractive index n1 to n2 with n2 > n1, the amplitude reflection coefficient is given by: r = (n2 - n1)/(n2 + n1) Consider a beam of light passing through a single pane of glass. There is a reflection at the front surface of the pane, with the...
  10. L

    Total Internal Reflection: Finding the angle?

    Homework Statement The figure below shows a ray of light entering one end of an optical fiber at an angle of incidence i = 51.0°. The index of refraction of the fiber is 2.05. Diagram link: http://www.webassign.net/walker/26-55.gif (a) Find the angle the ray makes with the normal when...
  11. Math Amateur

    Finite Reflection Groups in Two Dimensions - R2

    I am seeking to understand reflection groups and am reading Grove and Benson: Finite Reflection Groups On page 6 (see attachment - pages 5 -6 Grove and Benson) we find the following statement: "It is easy to verify (Exercise 2.1) that the vector x_1 = (cos \ \theta /2, sin \ \theta /2 )...
  12. L

    Calculating Reflected Pressures in Mach Reflection Region

    Hello guys, I want to compute reflected pressures in Mach reflection region. In Mach reflection, let's just think about the reflected, incident and merged pressures (of Mach stem). You know, the merged pressure is created by coalescing the incident and reflected pressures. Assuming that all...
  13. M

    Light Reflection: Path Length Difference?

    Homework Statement When light reflects from a thin film back toward the source, what is the path length difference? The Attempt at a Solution A. It is equal to twice the thickness of the film. B. It is equal to the thickness of the film. C. It is equal to half the thickness of the...
  14. P

    I'm a bit confused about rotation and reflection matrices

    Homework Statement I have a final coming up and I am a bit fuzzy on how to create a matrix that represents a rotation or reflection about a certain plane (in R3). Say we are given a rotation/reflection about either a plane or a line through two points T(v)=Av and we are told to find A. Do we...
  15. A

    Reflection and Transmission Intensity of randomly polarised light

    Homework Statement A randomly polarized beam of light hits a water surface at Brewster angle. What is the intensity of the transmitted and reflected beams? The refractive index of water is n = 1.33 Homework Equations The Attempt at a Solution Since the light is randomly polarised...
  16. P

    Total Internal Reflection

    Homework Statement Find the lowest angle of θ1 given the apex angle is 60°. Air (n=1) is on the outside and inside (n=1.5) ϕ is defined as 60 degrees. Homework Equations The Attempt at a Solution θc = sin-1(\frac{1.00}{1.50}) = 41.81° To my understanding, θ1 must...
  17. M

    Why reflection causes polarisation of light

    Hello all I know that polarisation of light can occur from reflection, and when the reflected ray is 90degrees from the refracted ray the relfected light is 100% plane polarised. So, my question is why is it that reflection causes polarisation of light? Thanks
  18. R

    Angle of reflection in a circle

    if a beam of light originates at point 1 aimed at point 4 will it reflect to point 2 then and point 8? as in the diagram? http://en.wikipedia.org/wiki/Enneagram_of_Personality
  19. L

    Simplification about the reflection of waves at a discontinuity.

    The following reffers to the reflection of waves at a discontinuity. (incident, reflected, and transmitted waves) Homework Statement (a) Simplify Aicos(k1x-wt)+Arcos(k1x+wt) = Atcos(k2x-wt) by eliminating common trig factors (recall cos(-θ)=cos(θ)), and dividing terms by Ai to express the...
  20. S

    Exploring Reflection: Light's U-Turns

    Does the light stop and turn back or does it interact with the surface and make a u turn.
  21. Math Amateur

    Reflections and Reflection Groups - Basic Geometry

    I am reading Kane's book on Reflections and Reflection Groups and am having difficulties with some basic geometric notions - see attachment Kane paes 6-7. On page 6 in section 1-1 Reflections and Reflection Groups (see attachment) we read: " We can define reflections either with respect to...
  22. Math Amateur

    Euclidean Reflection Groups _ Kane's text

    I am reading Kane - Reflection Groups and Invariant Theory and need help with two of the properties of reflections stated on page 7 (see attachment - Kane _ Reflection Groups and Invariant Theory - pages 6-7) On page 6 Kane mentions he is working in \ell dimensional Euclidean space ie...
  23. Z

    Composition of Two Isometries, Rotation & Glide Reflection

    Homework Statement R is a rotation around the origin by ∏/4, G is a glide reflection; the reflection is across y=x and the glide is by (2,2). Find the compositions R°G and G°R and characterize them. If you find a glide reflection, specify both the mirror line and the "glide" vector...
  24. N

    Geometric Optics: Speed of light and Reflection in a glass cube

    Homework Statement A large cube of glass has a metal reflector on one face and water on an adjoining face (the figure). A light beam strikes the reflector, as shown. You observe that as you gradually increase the angle of the light beam, if Theta is greater than 58.7 no light enters the water...
  25. E

    Determine coordinates of reflection given equation

    Homework Statement Find the coordinates of reflection of the point P (4,8) in the line y=-3/2 x + 14 Homework Equations y= -3/2x + 14 The Attempt at a Solution find a point on the line?
  26. Islam Hassan

    Optical Reflection: Difference Between a Mirror and a White Surface?

    If a surface is perceived as being white because it reflects all wavelenghts of visible electromagnetic radiation, how does this differ from a mirror surface which also reflects all impinging light? How is a mirror different from a white surface i) optically and ii) at the level of condensed...
  27. F

    Transmission line reflection coefficient

    Hello, I am looking at the following calculation for the reflection coefficient of a transmission line using the formula ((ZL - ZO) / (ZL +ZO) I can understand it all apart from the last part (0.355e^j). Can someone please tell me how that figure was gained from (-0.354 + 0.030j) (216 + j15...
  28. P

    Mirror Reflection: Tracking Sunlight with Arduino

    Hi I have build a setup where there are two RC motors to drive a mirror which is 2 dimensional. I have been thinking to write a program in Arduino such that after tracking (from solar tracker which i already made) the sunlight , the mirror should always be reflecting on a desired angle no...
  29. K

    Which Legs Experience Total Internal Reflection in a 45,45,90 Glass Prism?

    Homework Statement A 45,45,90 glass triangular prism (n=1.52) is surrounded by air. If a light ray comes into one of the legs (not hypotenuse) at a right angle which legs have total internal reflection?Homework Equations n_1sinx_i=n_2sinx_r The Attempt at a Solution i figured out that the...
  30. C

    Optics - Reflection of image from a moving mirror

    Optics -- Reflection of image from a moving mirror I have a dufficult question which I couldn't find an answer to, yet: If I am standing in front of a mirror - I can see my image, naturally. Now, let's say that the mirror is actually a very long train and it moves parallel to me . And...
  31. C

    Quick question about pressure radiation for reflection

    Homework Statement write pressure radiation for reflection in terms of force and area Homework Equations pradiation(reflection)=2I/c p=F/A The Attempt at a Solution pradiationreflection=2F/A is that correct? (im fairly certain I've solved this correctly but i just wanted to check)
  32. E

    Wave Equation after Reflection

    Hello all, Homework Statement We can represent a mechanical transverse wave by Y=Asin(kx-wt+∅). Now imagine this wave traveling (towards right as velocity is positive) and meeting up with two cases Case 1) Rigid wall. Case 2) Free end. The way gets reflected completely( ignoring transmission...
  33. S

    Solving schrodinger, reflection coefficient

    Consider the potential V(x) = \begin{cases} 0, & x < -a & (I) \\ +W, & -a < x < a & (II) \\ 0, & x > a & (III) \end{cases} for a particle coming in from the left (-\infty) with energy E (0 < E < W). Give the solution to the Schrodinger equation for I, II and III and use these to...
  34. M

    Ultrasound - intensity reflection coefficiant calculations

    Homework Statement The following table gives some specific acoustic impedances Tissue or Medium Specific acoustic impedance Air 0.00044 x 10^6 Fat 1.38 x 10^6 Water 1.5 x 10^6 Brain 1.58 x 10^6 Blood 1.59...
  35. S

    What is Brewster's Angle for Sunlight Reflecting on Water?

    Homework Statement As the sun rises over a still pond, an angle will be reached where its image seen on the water's surface(n=1.33) will be completely polarized in a plan parallel to the surface. i) Compute the appropriate incident angle(that is the polarization or Brewster's angle)...
  36. Math Amateur

    Linear Algebra Preliminaries in Finite Reflection Groups

    Linear Algebra Preliminaries in "Finite Reflection Groups In the Preliminaries to Grove and Benson "Finite Reflection Groups' On page 1 (see attachment) we find the following: "If \{ x_1 , x_2, ... x_n \} is a basis for V, let V_i be the subspace spanned by \{ x_1, ... , x_{i-1} ...
  37. Math Amateur

    Orthogonal Transformations _ Benson and Grove on Finite Reflection Groups

    I am reading Grove and Benson's book on Finite Reflection Groups and am struggling with some of the basic linear algebra. Some terminology from Grove and Benson: V is a real Euclidean vector space A transformation of V is understood to be a linear transformation The group...
  38. C

    What physics causes this mirror reflection?

    Hi, I just bought an iPad mirror screen protector and I'm really puzzled about how it works. You can see a video of the protector here The mirror quality is very good, of the order of 95% reflectivity, and it's not a metalized film as transmission is ~95% You can see in the video that...
  39. R

    How Do Rayleigh Waves Reflect When Transitioning from Solid to Liquid Surfaces?

    Hello everyone, I'm hoping someone will be able to shed some light on what I have to ask. Basically, I'm interested in the reflection of Rayleigh Waves/ Surface Waves as it travels and passes from a free surface to a surface in contact with a liquid. In particular, is there any written text or...
  40. P

    Reflection loss and refractive index

    Homework Statement "Calculate the reflection loss when a beam of radiant energy passes through an empty quartz cell assuming the refractive index of quartz is 1.55"Homework Equations I/I_i = ((n2-n1) / (n2+n1))^2The Attempt at a SolutionI'm taking the refractive index through the empty cell...
  41. E

    Whats the difference between reflection and scattering of photon? (QFT)

    Just read Feynmen's QFT and been wondering the difference between photon reflection by a perfect mirror and photon scatter by say a rough surface. In both cases, photons are said to be absorbed by electrons and re-emitted. But in reflection case, photons get to "preserve" its wave...
  42. F

    Anti-reflection coating and FULL reflection coatings

    Hello Forum, to obtain good anti-reflection at one specific wavelength, a layer of the right index of refraction is deposited on a certain surface. The layer thickness must be d=lambda/4... This achieves better transmission. If we used multiple layers we would get even better transmission...
  43. lavalamp

    Measuring emissivity of material based on reflection

    Homework Statement I have a university project that involves comparing various paints with regards to how they affect the insulating properties of houses. As part of that I would like to measure the emissivity of the paint for a variety of wavelengths. Unfortunately I can not simply heat...
  44. P

    Can some one Fully explain reflection for me, because i am reading my

    Can some one Fully explain reflection for me, because i am reading my book and i read about wavelets and I DONT UNDERSTAND THAT, so can some one explain it all PLEASE
  45. E

    Reflection: instantaneous or not?

    when light encounters a mirror, is it instantly reflected, or is it absorbed very briefly and then emitted?
  46. R

    Determining the Magnitude & Reflection Coefficient at 10 GHz

    A radar of 10 GHz produces an electromagnetic plane wave. Conductance is 4 S/m and dielectric constant is 81. How do you ding the magnitude and reflection coefficient? Also the percent of the incident energy that is reflected?
  47. P

    What Type of Mirror Creates an Inverted, Real Image Half the Object's Size?

    An object is placed 11 cm from a certain mirror. The image is half the height of the object, inverted, and real. 1/p+1/i=1/f ? Clueless because I don't know how to set up the equation int his kind of situation.
  48. I

    Diffuse Reflection vs. Scattering?

    Is there a fundamental difference between specular and diffuse reflection, or between diffuse reflection and scattering? I have heard various explanations that I am trying to sort out. (Please note that these "explanations" are not necessarily an accurate record of what was presented to me--...
  49. B

    Doppler Effect: Will the Frequency Change Upon Reflection?

    When a source emitting a sound of a specific frequency moves towards the face of a cliff at a speed. The frequency of the sound that reaches the cliff is for sure not the same as the frequency emitted from the source due to doppler effect. Will the frequency of the sound reflected by the cliff...
  50. N

    Reflection of a plane mirror and phase shift

    Homework Statement Hi I think I have confused myself: If I have a linearly polarized beam incident on a plane mirror with higher index, will the 180-degree phase shift change the direction of the polarization? Say, from lying in the 1st-3rd quadrant to lying in the 2nd-4th quadrant...
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