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. W

    On the clockwise rotation of the reflection coefficient with frequency

    It is well known that the evolution of the input reflection coefficient, ρ, of a LTI causal passive system with frequency, f, always presents a local clockwise rotation when plotted in cartesian axes (Re(ρ), Im(ρ)), e.g. in a Smith chart, as shown in the attached figure. It must appointed that...
  2. N

    How does photon react in reflection and refraction?

    I want to apologize first of i post at the wrong section, not very sure if this is the right place for this post. First question, does the photon get absorbed when it hit highly reflecting material like mirror ? What make them look so different from the other transparent object? And I just...
  3. hb20007

    F(-x) is a reflection over the y axis -f(x)

    f(-x) is a reflection over the y axis -f(x) is a reflection over the x axis Now, how do we represent a reflection over y=x?
  4. Z

    Understanding the Doppler Effect and Reflection in Motionless Media

    Hello everyone, Here is something I've discussed with some colleagues recently and that generated a lot of disagreement, so I wanted to bring the topic to Physics Forums to ask what is your understanding of the situations and wheter you agree with the "solution" I provide below or not. Imagine...
  5. G

    What is the Maximum Angle for Total Internal Reflection in a 30-60-90 Prism?

    Homework Statement Red light is incident in air on a 30o - 60o - 90 o prism as shown. The incident beam is directed at an angle of φ1 = 37.6o with respect to the horizontal and enters the prism at a height h = 26 cm above the base. The beam leaves the prism to the air at a distance d =...
  6. P

    Virtual boxes mirror reflection

    Homework Statement Finding lightpaths with given starting and ending points via one or more mirrors. In those kind of problems you try image someone pointing a laser with a very narrow beam at a certain direction to the mirror, so it will reach point B. For example: You are seeing a square...
  7. P

    A mirror reflection of a mirror reflection

    a mirror reflection Homework Statement Create a set-up, as shown in the Figure, consisting of two mirror tiles (A and B) and a bird face, facing to the right . Make sure the two mirrors are perpendicular to the table and parallel to each other. The situation shown is a front view of the...
  8. ShayanJ

    Details of total internal reflection

    Consider snell's law n_1 \sin{\theta_1}=n_2 \sin{\theta_2} ( n_1 and n_2 are real). We know that if n_2<n_1 , there exists an incident angle called critical angle that gives a refraction angle of ninety degrees i.e. \sin{\theta_c}=\frac{n_2}{n_1} . But if the incident angle is greater...
  9. A

    Exploring Total Internal Reflection: Why Does Light Path Through a 2nd Medium?

    Hi And Need Help The main Question is what happens to light and cause go into next medium as total internal reflection happens for incident angles higher than critical angle ? so the main question is why the light path throughout the second medium? We know when light travels from a medium...
  10. R

    Reflection and absorption in matte black vs. shiny black objects

    Hi, I'm confused about reflection and absorption in materials. Is glossiness of an object determined by roughness of its surface rather than its inability to absorb visible light? If there are dark-colored objects where one has a matte finish and the other has a glossy finish, does this mean...
  11. N

    Electric field Phase change upon rarer to denser reflection of an EM

    Can anyone please provide an intuitive explanation of why phase shift of 180 degrees occurs in the Electric Field of a EM wave,when reflected from an optically denser medium and also why the phase remains same on reflection from a denser to rarer medium? please try to explain on an atomic/sub...
  12. M

    Find angle required for total internal reflection of a beam of light

    Homework Statement An optical fiber consists of a glass core (index of refraction n1) surrounded by a coating (index of refration n2<n1). Suppose a beam of light enters the fiber from air at an angle θ with the fiber axis as shown in attached. (a) Show that the greatest possible value of θ...
  13. H

    Full reflection of wave function for E = V0

    I have seen discussions which suggests that there is no solution for the interval after the step in a step potential where E = V0. The set up is a potential step where E = V0, with an interval 1 defined as x < 0 before the step and an interval 2 as x > 0 after the step. Is the following...
  14. M

    Photonics Question - Laser and Total Internal Reflection

    Hello, this is my first post to this site. I had this idea a few nights ago, and I've been trying to wrap my head around it. Before I go ordering supplies to run some tests, I thought it would be worthwhile to gain some insight from you guys. Anyways, as you probably know, total internal...
  15. P

    Forces in a Quantum Reflection

    Hi folks, So everyone at some point studying QM deals with reflections from 1D finite potential wells using the TISE, but something that I never covered was how to talk about or calculate the forces involved in turning around that particle. I tried to work something out below, but I'm not...
  16. V

    Equation for object size relative to reflection?

    Homework Statement The situation below is based upon the image of an object in the presence of a sheet with a small hole and an object that reflects an image onto a screen when shined with a light. The problem is below: Write an equation that shows the relationship between the length of...
  17. V

    How Thick Should a Plastic Plate Be for Maximum Microwave Reflection?

    Homework Statement A plastic plate with refraction index of 1.5 is placed in the interior of a micro-wave oven which operates with a frequency of 2.5 x 10^9 Hz. If the micro-waves are perpendicular to the surface of the plate, what is the minimum thickness of the plate so that the maximum...
  18. A

    How does a photon reflect off a smooth surface?

    Hello, I was just reading optics and I thought that if photon doesn't has mass it can't be accelerated.. If it is so then how it gets reflected off a smooth surface, why don't it just passes from the plane. As any reaction force by the plane couldn't accelerate it , it mustn't rebond as...
  19. H

    Reflection of particles and light: different reflection surface types

    Hi, I'm interested in reflection of both particles and light off surfaces. My problem is associated with a model that I'm working on and can be divided into two parts as far as I see it. The first problem is the reflection of particles off the surface and the change in velocity due to...
  20. K

    Simple Transformation of a Function: translation, reflection, sketch

    Homework Statement Hi all. I am having trouble to understand the combination of transformation on a function: h(x)= a*f(b(x-c))+dHomework Equations The problem I am struggling with is the order of transformation; I do see that: f(x-c) is translation in the right since every event happen before...
  21. S

    Is Stefan–Boltzmann law valid for light reflection

    I know emissivity parameter of Stefan-Boltzmann equation is related to both "absorption" and "emission" of the material. But is it related to "reflection" property of an object? If not what is the parameter that makes an object shiny?
  22. I

    How does wave reflection work?

    this is a silly question but, how exactly does the reflection of a wave work? explain to me the mechanics/physics please. say you have a rope attached to a wall at one end. and at the other end there is a wave generator. a wave is generated and right when the wave front hits the wall, what...
  23. D

    Statistical physics reflection principle

    Homework Statement Consider a random walker in one dimension, which can take right or left steps with equal probability. Assume that the walker starts at the location k>0 and there is an absorbing wall at point labelled as 0, that means if the walker reaches 0 the process stops and he stays...
  24. A

    Total internal reflection inside a fiber optic cable

    Homework Statement A multi-mode fiber optic cable has a core diameter d = 115 mm, ncore = 1.42, and ncladding = 1.17. What is the largest possible angle θin relative to the surface normal that light can enter the fiber (i.e. pass from air into the fiber core) and experience total internal...
  25. Saitama

    Ray optics - Reflection from sphere

    Homework Statement A light ray parallel to the x-axis strikes the outer reflecting surface of a sphere at a point (2,2,0). Its center is at the point (0,0,-1). The unit vector along the direction of reflected ray is ##x\hat{i}+y\hat{j}+z\hat{k}##. Find the value of ##yz/x^2##. Homework...
  26. MikeGomez

    Does Quantum Mechanics Explain the Fuzziness in Light Reflection?

    From this video of a Feynman lecture: At 39:30 he (Feynman) draws a line from the eye to the mirror, and then continues the line through the mirror, to represent where the image appears to come from (it appears to come from behind the mirror). Here he is showing the classical way of...
  27. Y

    Help with vector calculus in reflection and transmission of plane wave

    This is not a homework, this is concerning reflection and transmission of electromagnetic wave ( plane wave) at a flat planar boundary between two media. But the work in question is pure vector calculus. I ultimately want to proof if ##\vec E_I=\hat y E_I## then ## \vec E_R## and ##\vec E_T##...
  28. jaumzaum

    Torque, Momentum and Reflection

    A light beam of frequency f hits a mirror of length L at a distance 3/4 L from one end, which is fixed but can rotate freely around the axis as shown. The mirror has mass m and can be considered a rectangular plate. The light beam hits (and fully reflects) the mirror at a rate of N photons per...
  29. Y

    Please check what's in the Ulaby book regarding reflection.

    Attached is a scanned of the page in question. This is regarding to Perpendicularly polarized plane wave. in equation (9.47a) at the lower left corner it is the distance ##x_i## to the origin. x_i=x\sin\theta_i+z\cos\theta_i\;\hbox {(9.47a)} That is not a distance. distance of ##|\vec...
  30. Y

    Question in reflection and transmission at oblique incidence.

    I am reading Griffiths p387. It is my understanding that \tilde E(\vec r,t)=\hat r E_0 e^{j(\omega t-kr)} Where ##\vec r =\hat x x+\hat y y+ \hat z z## is the positional vector from the origin to the observation point ( x,y,z). \Rightarrow\;\tilde E(\vec r,t)=\hat r E_0...
  31. Y

    Question of reflection and transmission of TEM wave in normal incidenc

    Suppose TEM wave in +z normal to a boundary on xy plane at z=0. We know E & H are tangential to the boundary. Let ##\vec E_i=\hat x E##, be the incident wave towards the boundary therefore incident H is ##\vec H_i =\hat z\times \hat x \frac {E_i}{η}=\hat y H##. I have a few questions: 1) How...
  32. J

    Any Conceptual Underpinning for Partial Reflection of Light (QED)

    Any Conceptual Underpinning for Partial Reflection of Light (QED)? I recently partially read Feynman's QED. At one point, he says "The situation today is, we haven't got a good model to explain partial reflection by two surfaces;..." (page 24--can visit Amazon "Look Inside" to read) My...
  33. W

    Calculate Reflected Radiance from Wave Facet

    When I view the sea surface for a few seconds (using a camera), some wave facets have very high radiance values. I understand that there is a distribution of slopes and that one can determine a statistical radiance distribution, but how do I calculated the reflected radiance from a single wave...
  34. S

    Polarization by reflection and Brewsters Angle

    Homework Statement A beam of light is reflected off the surface of some unknown liquid, and the light is examined with a linear sheet polarizer. It is found that when the central axis of the polarizer (that is, perpendicular to the plane of the sheet) is tilted down from the vertical at an...
  35. S

    Reflection of Light ~ Mirror on one side, surveillance on the other.

    Question In many department stores, large plane mirrors have been placed high on walls or on projections from ceilings. These may be one-way mirrors that are designed to allow one-way surveillance of the store. From one side, this surface looks like a mirror, but from the other side, the...
  36. P

    Δp for total reflection and absorbtion of E&M radiation explanation?

    The equation for the change in momentum for total absorption of electromagnetic radiation is ΔU/c and that for total reflection is (2ΔU)/c. How could the momentum of electromagnetic radiation change if it is massless and travels at a constant speed c? Is the ΔU just a representation of a change...
  37. 7

    Transmission and Reflection on a potential step

    Lets say we have a potential step with regions 1 with zero potential ##W_p\!=\!0## (this is a free particle) and region 2 with potential ##W_p##. Wave functions in this case are: \begin{align} \psi_1&=Ae^{i\mathcal L x} + B e^{-i\mathcal L x} & \mathcal L &\equiv \sqrt{\frac{2mW}{\hbar^2}}\\...
  38. K

    Exploring Visible Light: Reflection & Energy

    how does visible light carry with it? does this energy increases with increase in number of reflection?
  39. E

    Wave Equation After Reflection

    What do the components of the following equation represent : http://www.mediafire.com/view/?0we6f9jkw26qi9o To be clear, this represents a wave of the form Acos(kx-wt) after being reflected off a wall. I understand that the ∅ represents the phase change of the wave after hitting the...
  40. I

    Reflection of sound depends on frecuency?

    Hi! I need some help understanding something related to sound. I am currently studying a book called Sound Propagation. An Impedance Based Approach, by Yang-Hann Kim. There is a part where he talks about reflection and transmission of acoustic waves on a flat surface of discontinuity. He gets...
  41. E

    Optics: Total Internal Reflection with Triangular Prisms

    Homework Statement When the striking ray is held perpendicular to the prism, there are four general configurations possible (in the attachment below). Use the figure on the next page to determine analytically which of these four configurations will result in total internal reflection of the...
  42. H

    Periscope reflection, but it seems backwards

    This is the question and the answer choices. I thought it would be mirror one creates E and mirror 2 creates F, but It's not... help?
  43. C

    Reflection of a plane mirror at a focal point

    I am trying to interface a detector system to a FT-IR spectrometer. The spectrometer uses off-axis parabolic mirrors to focus light in the center of a sample compartment, where it diverges and again strikes an off axis parabolic mirror, focusing it on a detector. I would like to place a plane...
  44. D

    How does optical reflection work?

    How does reflection work in non-metals and metals? If you take, for example, a polished brass surface (or whatever really) and an incident photon, is the photon being absorbed and re-emitted by an atom at the surface of the reflective brass? If so, how is it that the re-emitted photon is...
  45. M

    Question on the Law of Reflection

    The law of reflection states that the angle of incidence equals the angle of reflection. In the event of a beam of light reflecting upon a horizontal surface, the incidence angle is 45 degrees (as a variable, 45 degrees will be represented by A). The angle formed by the reflection will...
  46. P

    Transmission and reflection coefficients

    Hi when using the WKB approx, is there a general method to find these Refelction and Transmission coefficients, I have tried looking in books and on the net and I can't find a 'general' formula, they tend tjust to be quoted. I know that |T|^{2}+|R|^{2}=1 . And generally that T=...
  47. N

    Simple reflection and translation question

    Homework Statement If the graph of 1/x is reflected in the y-axis, translated 3/4 units to the right and 2 units up, the resulting graph would have the equation... A) 1/(x-2) + 0.75 B) 3/(4x) +2 C) 2 - 1/(3/4x) D) -1/(4x-3) + 2 E) 1/(3-4x) + 2 2. The attempt at a solution So the general...
  48. R

    Use the law of reflection and index of refraction to find apparent d

    Homework Statement See image Homework Equations n1sin(theta1) = n2sin(theta2) 1/s + 1/s' = 1/f The Attempt at a Solution My question is for the second part. I think I've figured out why I got it wrong, but I'm not sure. So since the object distance (s) should be approximately 21 cm, then...
  49. O

    Relationship between Polarizing Angle and Angle of internal reflection

    Homework Statement The critical angle for total internal reflection for a substance is 58.0°. What is the polarizing angle for this substance? Homework Equations Index of refraction: n = 1 / sin(θ_{c}) and n = tan (θ_{p}) The Attempt at a Solution So I plugged in the numbers for...
  50. T

    Passive Adiabatic Effect: Cold sky reflection on IR imagery.

    I am currently in training to become an analyst using thermal imagery. In the studies I have been introduced to cold sky reflection on thermal imagery, however the instructor explained it as a surface 'reflecting the cold from the sky' which, as far as I'm aware, doesn't fit with the second law...
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