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

    Reflection of Pulses (Theoretical Problems)

    Homework Statement We begin by considering the forces exerted on a ring that is connected to a spring and that is free to slide along a rod TOP VIEW: The diagram is top view Diagram Description (sorry don't have a pic): A pulse traveling towards a free end (has NOT reached the boundary...
  2. L

    Mirrors and Reflection: The Mysterious Maths

    I wasn't sure where to post this and i apologize if its already been posted. I think there is an obvious answer for this but for some reason I cannot figure out a consistent answer. I am looking for a mathematical answer more than anything else. When you look in a mirror you image is switched...
  3. T

    Reflection and Transmission (Waves in strings)

    Homework Statement Two copper wires, one 1.0 mm in diameter and 1.0 m long, the other 2.0 mm in diameter and 2.0 m long, are joined together end-to-end and hung vertically. In order to tension this compound wire, a block is suspended from it. It is found that a transverse pulse takes 50...
  4. Y

    Why does Fresnel's law only use 2 boundary conditions compared to Maxwell's 4?

    We use only 2 boundary conditions in driving Fresnel's laws, whereas Maxwell's equations provided 4 conditions (2 were identical to other 2). What is the intuitive explanation for this redundancy? which boundary conditions turned out to be equivanlent to each other.
  5. N

    Regarding Total Internal Reflection

    Regarding "Total Internal Reflection" Hi, and thanks in advance for viewing this post. I'd like to type out the question first; Q: Consider the optical interface between crown glass and ethanol. a) Under what conditions would total internal reflection be possible at this interface? Illustrate...
  6. J

    More questions on Reflection

    1. How does scientists know that the light from far distant heavenly bodies are actually from those, or some kind of reflection? 2. If a red object reflects only red frequency light, why I do not see red light from that object to the surrounding?
  7. H

    Bragg Reflection w/ X-Ray tube voltage

    Homework Statement When a beam of monochromatic x-rays is incident on a particular NaCl crystal, Bragg reflection in the first order (ie w/ m=1) occurs at theta=20 degrees. The value of d = .28nm. What is the minimum voltage at which the x-ray tube can be operating? Homework Equations...
  8. J

    Exploring Light Absorption & Reflection: How Much is Too Much?

    As I know, a black substance absorbs all light and a white substance reflects all light. Can I say, in a black substance, the electrons are in a high energy state, compared to a white substance? And how much light energy it can absorb? There has to be a limit to it, right? So, shouldn't a...
  9. M

    Is nature a reflection of who we are as individuals?

    I once heard a very interesting thought through a zen story, that said "Nature reflects the true self." So simple, yet I had felt that before, but didn't know how to explain so crispe and clear. Now, the problem for me comes with the question not doubting this thought, since we have our own...
  10. cepheid

    What is the Divisibility Rule for the Reflection of an Integer?

    "Reflection of an Integer" I haven't encountered this before. I'm not sure how to approach it. At this point it's not even clear to me why the result should only be divisible by one number in *every* case. The reflection of a positive integer is obtained by reversing its digits. For...
  11. W

    What Is Reflection & How Does Light Reflect?

    How does light reflect? I am going to speculate below and maybe one of you all who have more experience in Physics can tell me if I am correct or give me a reference. I have an undergraduate degree in EE so you can talk to me as someone with a little college physics but (obviously by what I am...
  12. J

    Explaining reflection and refraction in atomic level

    https://www.physicsforums.com/showpost.php?p=899393&postcount=4 describes why photons are slower in some medium. After reading it, I've few more questions: When a photon hits an electron, if it absorbs the photon and reemits, here's my questions: 1. How does refraction possible? The...
  13. T

    Why Does Light Reflect? - Unraveling the Mystery

    Why does light reflect? I know that it does, and the rules and uses connected with this, but WHY does the em wave actually change direction on hitting a shiny surface? Is it at an atomic level? Cheers Tom H
  14. Repetit

    Reflection and radiation pressure.

    Hey! When a photon is reflected off an interface doesn't it deliver some of it's momentum to the object that it hits due to radiation pressure? If so, shouldn't the reflected light have a longer wavelength (smaller wavenumber) than the incident light? Is this effect present, but just so small...
  15. I

    Simple radio wave reflection question

    heres a simple question I somehow couldn't find an answer on the internet. we know radio waves only reflect (significantly) when it strikes an object with size greater than the wavelength, but I'm not sure what exactly defines the "size" of the object. For example, if I were to confine a...
  16. F

    Index of refraction when total internal reflection ceases

    light refractions problem I don't even know where to start with this problem. Can someone please help me out? As shown in Figure P22.49, a light ray is incident normal to on one face of a 30°-60°-90° block of zircon(n= 1.923) that is immersed in water. Figure P22.49 (a) Determine the...
  17. S

    Reflection of Light: Understanding the Angle of Incidence & Reflection

    If reflection of light is an interaction with atoms how we get always angle i=angle r?
  18. C

    Polarization change upon reflection

    Hello, I'm trying to understand how exactly light changes its polarization when reflected from a mirror, for example. I'm quite familiar with Fresnel's equations and resulting coefficients, but I'm not sure how the phase of the TE and TM polarizations changes upon reflection. For example...
  19. S

    Why does my HDTV appear red when reflecting light?

    I noticed that when my lamp reflects off of my HDTV, it appears red. It seems that the more light that is reflected into it, the redder it gets. I'm figuring that the green and blue line of the phosphor dots (I think that's the name for the tiny red, green, and blue lines on a screen) are not...
  20. N

    Orthogonal Matrices: Rotation & Reflection

    We know that if M is an orthogonal matrix,then DetM=(+-)1 When Det M=1,thee transformation is a rotation.And for reflection about anyone o all three axes DetM=-1. I did this.. But I did not know that information:When Det M=1,thee transformation is a rotation.And for reflection about anyone...
  21. T

    Why the reflection and transmission?

    in solving the time-dependent Schrödinger's equation for the delta potential, one obtain a set of non-normalizable solutions. form the boundary condition and comparing the coefficients of the solution, one obtains the probability of transmission and reflection. However, how can one be sure...
  22. P

    How does a Reflection diffraction grating work?

    Hello, I am wondering how does a reflection diffraction grating work. Most physics text simply ignore this topic or talk in very ambigious terms. I understand that in transmission diffraction grating, you have parallel grooves so that light can pass through and produce an interference pattern...
  23. E

    Optics/ total internal reflection (non-trivial at least for me)

    Homework Statement The refractive index of the Earth's atmosphere is: n=1.01+(alpha)(R-r) where (alpha) is a constant, r is radial distance from Earth's centre and R is the Earth's radius. By considering a path comprising a series of total internal reflections or otherwise, find a value of...
  24. 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...
  25. A

    Is the Book Wrong About Total Internal Reflection and Snell's Law?

    As the angle of incidence increases, the angle of refraction becomes larger. Should the underlined word be decreases? why? I think I've found a mistake in the book because according to snell's law of refraction n1sin(theta)1=n2 sin(theta)2 right? If n1>n2 then (theta)1<(theta)2 Wait, I...
  26. S

    Frustrated total internal reflection

    While making calculations of FTIR/tunneling isn't that hard, I don't understand the phenomenon, and therefore there are some predictions I'm unable to make. So I have some questions (or it's probably just one). If you have a prism with refractive index n in vacuum, total internal reflection...
  27. M

    How can I calculate the angle of a tilted mirror to see my reflection?

    Homework Statement You stand 1.80 m in front of a wall and gaze downward at a small vertical mirror mounted on it. In this mirror you can see the reflection of your shoes. If your eyes are 1.95 m above your feet, through what angle should the mirror be tilted for you to see your eyes...
  28. S

    Reflection of different metals

    Homework Statement Having done an experiment measuring the intensity of light reflected from copper, lead, zinc and iron, i found that copper reflected the most light, then iron, then zinc, then lead. Now i have to explain it and I don't really know how to ! The Attempt at a Solution...
  29. T

    Finding the Angle of Incidence in a Plane Mirror: Reflection of Light Homework

    Homework Statement A person stands 3.6m in front of a wall that is covered floor to ceiling with a plane mirror. His eyes are 1.8m above the floor. He holds a flashlight between his feet and manages to point it at the mirror. At what angel of incidence must the light strike the mirror so...
  30. G

    Reflection of a mechanical wave

    when a mechanical wave is reflected by a fixed support it experiences a phase change of pi ... without getting into maths can i qualitatively prove this ? i cannot analyse how the forces will be acting .
  31. D

    Why Does Wave Reflect at Impedance Discontinuity?

    Why does a wave reflect when it meets an impedance discontinuity? And why is there a 180 degrees phase shift of the reflected wave when the transmission line finished with short circuit and no phase shift when the far end of the line is opened?
  32. A

    E&M: Energy Transported over medium w/ total internal reflection

    Homework Statement In the case of total internal reflection, show that the average rate of energy transport across the boundary is zero. Homework Equations None Provided The Attempt at a Solution All that I have come to is that I should use some form of the following method to find...
  33. cepheid

    What Are the Miller Indices for the Bragg Reflections?

    Homework Statement An alkali halide is studied with the Debye-Scherrer technique and Cu K_{\alpha} radiation. The Bragg angles for the first five lines (in degrees) are 10.83, 15.39, 18.99, 22.07, and 24.84. Calculate (a) The lattice parameter (b) The Miller indices for the planes producing...
  34. B

    Calculate the reflection coefficients of the load and the source impedances

    Hi there, I am new member to this forum. I am taking online courses, in order to get my degree. For all of the problems, the transmission line in the problem has a characteristic impedance of 50 ohms and is one quarter wavelength (an electrical length of 90 degrees) at the frequency of the...
  35. N

    Reflection of light upon ourselves

    I was thinking... When you shine a light in a mirror, the surface is reflective enough to produce a smooth image. Are we reflections of light, or does light simply shine on us to light us up? It would seem like when light hits mass, it is reflected, which produces the images that we see. And if...
  36. V

    Reflection Grating Homework Solution

    Homework Statement http://img244.imageshack.us/img244/6852/phys24xy.png Homework Equations d=1/N d*sin(theta)=m*(lambda) The Attempt at a Solution d=1/1970 d=.0005076 .0005076*sin(theta)=2*600e-9 sin(theta)=.0000012/.0005076 arcsin(.002364)=.135º *sigh*
  37. 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...
  38. T

    Sinusodial wave motion and reflection

    Homework Statement Okay, I've got a question that's been bugging me for the longest time. I've got a string attached to a wall at one end (the other end is free to move, though) and it has a sinusoidal wave traveling to the right and hits the wall at x = L and reflects. I'm supposed to...
  39. F

    MgF2 Thin Film Reflection: Visible Intensification?

    Homework Statement A thin 1.00x10^-5 cm-thick film of MgF2 (n=1.38) is used to coat a camera lens. Are there any wavelengths in visible spectrum intensified in reflected light? Homework Equations thickness = wavelength/4n (n is refraction index) ? The Attempt at a Solution I am...
  40. lemma28

    Layman Reflection on Classical and Quantum Mechanics

    We have 1 particle. Classical Mechanics says: If I know the initial state I can predict with absolute certainty what position (etc.) it will have the next second. Quantum Mechanics says: I don't know the position the particle will hit. But If I know the state I can tell you the possible future...
  41. C

    Understanding Reflection in 3D Space: Finding Point Q | Homework Equations

    Homework Statement The point Q is the reflection of P(-1,3,4), in the plane with equation 2x-y+z=1. Determine the coordinates of Q Homework Equations The Attempt at a Solution Well I am not really looking for a solution. I just want to know what I am trying to find. What is a reflection in...
  42. W

    Reflection and Quantization of Energy Levels

    From what I have been reading, the reflection of light from an object, like th eyellow color of sulfur is the same phenomenon as Rayleigh scattering. It seems that the electrons receive the incoming photon and are raised to a higher "virtual energy state." When they return to the ground state...
  43. S

    Total internal reflection question

    How do the angle of incidence relate mathematically with the angle of reflection after the critical angle, that is, in a TIR? Say we have a person standing at the bottom of a swimming pool, if we take the n for water as 1.33 and for air as 1, we get the critical angle of 48.75 degrees. When the...
  44. L

    Solve the Reflection of Lake-Bed: A 10m Deep Diving Challenge

    hi, i got a real problem. i have a question here and have absolut no clue what i have to do and which equation i have to use... ( for my shame, i was sick at that time we done it in school..) question: A diver is at the bottom of a lake, which is 10m deep. if he looks straight up he...
  45. N

    Reflection problem (optics)

    Homework Statement I have a transparent plate (call the thickness t and refractive index n), it has a scratch at a point A. A microscope objective (M, positive) images the point A in A' at a distance D from the objective. If we move M a certain distance d down (without changing focus, meaning...
  46. P

    How Do Mass Attachments Affect Wave Reflection and Transmission on a String?

    Homework Statement Consider an infinitely long continuous string with tension \tau. A mass M is attached to the string at x=0. If a wave train with velocity \frac{\omega}{k} is incident from the left, show that reflection and transmission occur at x=0 and that the coefficients R and T are...
  47. S

    SONAR and reflection head on

    Two submarines are underwater and approaching each other head-on. Sub A has a speed of 12 m/s and sub B has a speed of 17 m/s. Sub A sends out a 1520 Hz sonar wave that travels at a speed of 1522 m/s. ... I already solved for this question ... ... What is the frequency of the sound detected by...
  48. K

    Photon Reflection & Transmission: Calculating Probabilities

    qw: A photon is incident on a beam-splitter. At high light intensities, the beam-splitter is known to transmit 30% of the incident light, and reflects 70% of the incident light. Calculate the probability that the photon is refected, and the probability that the photon is transmitted. how do i...
  49. S

    Transmission and Reflection Coefficients

    Consider the step potential defined by V(x) = 0 if x < 0 Vb > 0 if x=> 0 a) Compute te relfection and tranmission coefficients for a particle of energy E > Vb approaching from th left For x < 0 Schrodinger equaion since V = 0 -\frac{\hbar^2}{2m} \frac{\partial^2 \psi}{\partial x^2}...
  50. T

    How Does the Index of Refraction Change Across Different Materials?

    In Figure 33-48a, a light ray in a liquid (n = 1.61) is incident at angle 1 on a boundary with an underlying material, into which some of the light refracts. There are two choices of underlying material. For each, the angle of refraction 2 versus the incident angle 1 is given in Figure 33-48b...
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