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. Danny Boy

    I Why is reflection coefficient defined this way

    In Griffith's "Introduction to Quantum Mechanics, second edition" he states: For the delta-function potential, when considering the scattered states (with E > 0), we have the general solutions for the time-independent Schrodinger equation: $$\psi(x) = Ae^{ikx} + Be^{-ikx}~~~~\text{for }x<0$$ and...
  2. nmsurobert

    Plotting reflection coefficient

    Homework Statement plot the magnitude |r| of the reflection coefficient as a function of incident angle from 0 to 90 degrees with a step size of 1 degree for the following cases: (ill only post one) A transverse electric plane wave in incident from air to glass Homework Equations r = (n1cosθi...
  3. B

    Transmission line and infinite reflection coefficient

    Hello, I am taking some microwave engineering courses and was trying to explain the concept of reflection coefficients to my friend, but he asked me a question I am unable to answer... So we know that given a transmission line with characteristic impedance Z_0 terminated with a load impedance...
  4. D

    Matrix Reflection Homework: Find Orthogonal Matrix in R3 Plane

    Homework Statement Let u1,u2,u3 be an orthonormal basis for R3 and consider M as the plane with equation x1+2x2-2x3=0. Find the matrix of orthogonal reflection in that plane with respect to the given basis. Homework EquationsThe Attempt at a Solution In previous exercises , I had a matrix A...
  5. I

    Potential barrier, reflection coefficient

    Homework Statement Electrons are pushed into a grounded metal tube A by the kinetic energy of 100 eV. After having gone through the tube it passes into another tube, B, at some distance from A. Tube B is kept at a potential of -50V. Calculate how many of the electrons are reflected back into...
  6. T

    Question on laser reflection (pic included)

    Good morning all, I'm currently working in some undergraduate research involving lasers and recently had the opportunity to play around with a few that my research professor has at our disposal. I've included a picture below of a strange phenomenon that has me a little puzzled, but then again I...
  7. D

    Light reflecting off sphere -- Momentum transfer

    Homework Statement Suppose light of momentum -P\hat{\textbf{k}} is shone on a sphere of radius R. What is the momentum transferred onto the sphere? Homework Equations The Attempt at a Solution I think the transferred momentum upon reflection is given by (-2P\hat{\textbf{k}} \cdot...
  8. R

    Interference from reflection off water across a lake

    #89 chapter 35 A microwave transmitter at height a above the water of a wide lake transmits wavelength lambda to a receiver across the lake height x above the water. Reflected wave interferes with waves arriving directly. Assumptions: width of lake D is much greater than a or x, and lambda is...
  9. D

    Fresnel zone and reflection of light on surfaces

    In a Scientific American article from 1968 in which he explains classically how light interacts with matter, Victor Weisskopf states that "the reflection of light on the surface of a solid or liquid involves only the oscillators (electrons) located in a small, pillbox-shaped volume at the...
  10. D

    Reflection and absorption of UV light

    Hi,I have a question when I was reading this website: http://www.webexhibits.org/causesofcolor/7F.html It explains how melanin works to protect us against UV light. From high school physics course we know that black absorbs light while white reflects. I understand when melanin accumulates,more...
  11. M

    Transmission and Reflection Amplitude for Delta Potential SE

    This is not a homework question per se, but it's a simple enough computation question from some notes I'm reading that I think it belongs in this section. I will do my best to keep to you guys' formatThis is not a homework question per se, but it's a simple enough computation question from some...
  12. Vannay

    EM wave reflection: phase shift off of conductor

    I know there is a pi phase shift when going from an area of lower index of refraction to higher. Is this phase shift still pi when going from a non-conducting dielectric with index of refraction n and reflection off a "good" conductor?
  13. Seismic101

    Does reflection accompany refraction in Snell's law?

    If the the angle of incidence of an incident ray is less than (or equal to) the Critical Angle, the ray is refracted, but do we still get some reflection from this same incident ray?
  14. M

    How can I find the minimum index of refraction?

    Homework Statement We look at the center of one face of a solid cube of glass on a line of sight making 55° with the normal to the cube face. What is the minimum refractive index of glass for which you will see through the opposite face of the cube? (Hint: see through will be possible if the...
  15. C

    What Index of Refraction is Needed for a 104nm Coating to Cancel 550nm Light?

    Homework Statement You are designing a thin transparent reflective coating for the front surface of a sheet of glass. The index of refraction of the glass is 1.52 and when it is in use, the coated glass has air on both sides. Because the coating is expensive, you want to use a layer that has...
  16. F

    Reflection of Waves and Formation of Standing Waves

    I have three doubts in regard to waves on a string which I will try to make as clear as possible. For this purpose, I have considered a general wave: $$y_i=y_0\sin(\omega t - kx)$$ (1) If a wave pulse: $$y = y_0 e^{\frac{-1}{T^2} \left(t-\frac xv \right)^2}$$ is incident against a rigid...
  17. RJLiberator

    Do Seismic Reflections Reveal Velocity Information in Layer 3?

    Homework Statement The question is set up by a diagram. It has: Layer 1 velocity = 6km/s Layer 2 = calculated velocity of 7.58 km.s Layer 3 = reflection The angle of the source in layer 1 is 34 degrees, the angle in layer two is then 52.33 degrees The source then reflects off of layer...
  18. J

    Total Internal Reflection explained with Quantum Mechanics

    Is there an easy explanation of total internal reflection of light using Quantum mechanics(or QED)?
  19. Corwin_S

    Calculate the desired incident polarization of a light beam

    Hi I want to calculate the necessary incident polarization of a light beam at a given angle of incidence (theta_i) that reflects off BK7 glass (n = 1.5168) and is linearly polarized (i.e., 45 degrees). I know how to do similar calculations for incident natural unpolarized light, but not in the...
  20. E

    Wave reflection and refraction, relations between angles

    Hello! This post is strictly related to my previous one. Let's consider the same context and the same image. Regarding the oblique incidence of a wave upon an interface between two dielectric, all the texts and all the lectures write an equation like the following: e^{-j k_1 y \sin \theta_i} +...
  21. N

    How reflection and refraction of light are expressed at the particle level?

    How reflection and refraction of light expressed at the particles level ? Thanks in advance
  22. D

    Magnification at a Different Distance from Mirror?

    Homework Statement The focal length between a person and his mirror that produces a magnification of 1.50 when his face is 12.0 cm away is 0.36 m. He then moves to a distance of 3.7 times the focal length away from her mirror. What is the magnification now? Homework Equations di/do=m...
  23. L

    Reflected Light at 3D Angle: Shift in Polarization

    I've searched high and low for answers to this, and a friend of mine finally pointed me in the right direction. I decided to write a post about it so hopefully others who have the same question will find the answer more easily. When linearly polarized light is reflected at a 3D angle, the...
  24. A

    Reflection and refraction: the same thing at the atomic level?

    I got cornered in a discussion on the internet... I am not sure if I am right or not (I thought I was when I started). If you guys here tell me I am wrong, I have no problem admitting if I am indeed wrong first... person 2 said "Refraction =/= reflection. The atmosphere is colorless because...
  25. J

    Reflection of wave at open end (boundary condition)

    Hello! I need to understand one seemingly simple thing in wave mechanics, so any help is much appreciated! When a pulse travels to the right toward an open end(like a massless ring that is free to oscillate only in the vertical direction), then when the wave reaches the end it gets reflected and...
  26. merlyn

    Reflection Coefficient: Steps 4 to 5 Explained by Drforbin

    Hi all, Great forum. I really don't know if this is the proper place for this, so if it is not please forgive me. I have been researching reflective coefficients in transmission lines. I understand everything except steps 4 -> 5. Perhaps it is a lacking in my math skills but could someone show...
  27. M

    Progressive harmonic wave & reflection / transmission

    Homework Statement An incident wave frequency f =500Hz , power Wi = 50 W and amplitude Ai= 5 mm spreads to the positive x in a linear density rope u1 unknown. When the wave encounters another rope ( attached to the first at a point P) density linear u2= 64 g/m (such as u2>u1 ) , The...
  28. A

    Window reflection when dark out side act like mirror

    Why is it that when a light is on in a room with a window made out of glass, and it being dark out side the window. That you cannot see through the window and instead see light being reflected form the room around you. And vice versa when it is darker inside the room and brighter out side you...
  29. cainko

    MC (multiple choice) question about total internal reflection

    Homework Statement There is an optical fiber.A light ray enter it at i°.Total internal reflection occur at X. What are the necessary conditions for the light ray to travel along the core of the fiber? (I have canceled B and D already.) A.n1>n2 and angle i should be greater than a certain value...
  30. S

    How Does Light Reflect in an Ellipse to Connect Its Foci?

    I needed the proof of this:if a ray of light passes from one focus of an elipse after reflection it will pass the other focus.please i need the one only using the fact that i=r ( not the fermat rule)
  31. lilknaap

    Reflection coefficient S11 vs Resonator animation

    Hello, I'm trying to do an animation of a photon being absorbed by a resonator vs. the corresponding S11 plot being plotted against frequency. Can anyone give suggestions on how to go about this. As the photon goes through Vin, at other frequencies it will be reflected and probed at Vout. This...
  32. B

    Finding the distance of reflection in a mirror

    Homework Statement A student wants to find the position of an image in a plane mirror. She sets up the plane mirror with a pin placed vertically a few centimetres in front of it. To find the image the student looks into the mirror at an angle a little further along the mirror. She can see the...
  33. kelvin490

    Question about intensity of EM waves

    For electromagnetic wave if it's reflected from a perfect conductor standing wave can be form. I wonder why Poynting vector can be used to describe the intensity of standing EM wave. (see p.19 of http://web.mit.edu/viz/EM/visualizations/coursenotes/modules/guide13.pdf ). From some textbooks...
  34. C

    Reflection of particle between Inertial frames in SR

    Homework Statement Suppose a frame S' is related to S by a boost in the y direction by v. Imagine a wall is at rest in the S' frame along the line y'=-x'. Consider a particle moving in the x'y' plane that strikes the surface and is reflected by the usual law of reflection θ'i=θ'r. Find the...
  35. KaseyKC

    Deriving the law of reflection

    I'm trying to derive the law of reflection for Electromagnetic Waves and Optics. I'm using some lecture notes that my university provided. I'm confused as to why the two sine functions are changed to cosine functions as you don't do the same when you are deriving Snell's law. Refer to attached...
  36. X

    Polarization change upon Reflection

    Hello, I am trying to determine how an electromagnetic wave changes polarization upon reflection off of an arbitrary object. Here are my confusions in particular. 1. My assumption is that the change in polarization is very much dependent on the geometry of the object, but I don't know the...
  37. H

    Transmission and Reflection amplitude

    To calculate Transmission and Reflection amplitudes (t and r), say in the figure below which is composed of three regions, first we have the solution of Schrodinger equation in each region as: \psi _i=A_i |i> +B_i |-i> ; i=I,II,III. It seems that by matching the three wave functions and their...
  38. wood

    Quantum - determine reflection coefficient

    I am working through a past exam paper and this one has me stumped 1. Homework Statement Consider a particle of mass m with kinetic energy E incident from the left upon a step-up potential: $$U(x)=\begin{cases} 0 & \quad \text{for } x <0\\ V & \quad \text{for } x>0\\...
  39. P

    Which causes an object to become invisible, regular or diffused?

    When an object becomes invisible when it undergoes “regular” or “diffused” reflection?
  40. moriheru

    Understanding Reflection Planes in Diatomic Molecules

    My source is Walter A. Harrison:"Applied Quantum Mechanics" Section 5.4 p.83. When studying diatomic molecules such as N_2 one may make use of the high symmetry of the molecule with relfection planes σx,y,z. In Harrison it is said that each molecular orbital can be chosen to be even or odd under...
  41. S

    Why no decoherence after reflection from metal film

    When photons reflect from a mirror coated with, say, an aluminium film... the reflection is presumably down to their interactions with free electrons in the metal (and each electron is in an unknown state before and after). Yet the interference does not go away if a mirror is inserted in one...
  42. O

    Complex reflection and transmission coefficient of EM waves

    I have a question about complex reflection and transmission coefficients. For example, I am modeling a wave in air (medium 1) ## \varepsilon = \varepsilon_0 ## reflecting on, and transmitted to, a medium 2 with ## \varepsilon = \varepsilon' -j \varepsilon'' ## If the wave would have traveled...
  43. B

    Difference between sound echo and mirror reflection

    Homework Statement Why is is that when we look in a mirror we expect to see a reflection equally as bright as the real image, but when we stand in front of a cliff and clap our hands we don't hear an echo as loud as the original sound? Homework Equations R = (z2 - z1)/(z2 + z1) The Attempt at...
  44. U

    Why is there reflection in 222 plane of Silicon?

    We know that silicon has a FCC lattice with basis at [0,0,0] and [1/4,1/4,1/4]. The structure factor is S_{(hkl)} = \left[1 + e^{i\pi(h+k)} + e^{i\pi(l+k)} + e^{i\pi(h+l)} \right] \left[ 1+e^{i\frac{\pi}{2}(h+k+l)} \right] which should be zero for (222) plane. But measuring it carefully...
  45. R

    Reflection of Electromagnetic Radiation in Dense Materials

    Hello there, Here is an elementary explanation about 'Free end reflection': http://www.physicsclassroom.com/mmedia/waves/free.cfm My question is: Say we radiate from a certain direction a rigid not hollow object, that is surrounded by gas or by vacuum, with electromagnetic or other type of...
  46. D

    How to Optimize Sound Reflection with Multiple Types of Reflectors?

    I have 2 types of sound reflectors on the image attached. The angles are not proportional but you should get the idea. The black circle is the source, the black lines are the waves and the red lines are the reflections of the waves emitted by the source. My target is to reflect the sound waves...
  47. F

    Vector Reflection Across y=2x: Solving with Rotation and Change of Bases

    Homework Statement Find the (exact) reflection of the vector v = (5, 1) across the line: y = 2x. Hint: A sketch of v and the line may suggest an approach. Homework Equations The Attempt at a Solution I found the matrix -3/5 6/5 4/5 2/5 which seems like it gives the reflection across y=2x...
  48. K

    Frustrated total internal reflection superluminal

    When light encounters a boundary between a dense medium (glass) and a less dense one (air), it may undergo total internal reflection. But if there is another glass a short distance away, some light will jump the forbidden region by a tunneling process and enter the second glass medium. This jump...
  49. D

    How can we explain continuous absorption / emission?

    I am familiar with the explanations for atomic absorption and emission line spectra and how the existence of discrete, fixed energy levels can give rise to the absorption/emission lines that are seen at only very particular frequencies of EM radiation. However, I have no intuitive understanding...
  50. Suraj M

    Refraction through a glass slab + reflection off a concave mirror

    Homework Statement An object is placed 21 cm in front of a concave mirror of radius of curvature of 10 cm. A glass slab of thickness 3 cm and RI =1.5; is then placed close to the mirror. Find the position of the final image. Take distance of closer side of block as 1 cm from the mirror...
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