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. G

    Internal reflection equation question

    As you can see we have 3 media here. Only focus on the glass and coating medium. Assume an incident ray comes from the air medium and is refracted inside the glass and then it is refracted again in the coating medium. The x angle is the angle inside the glass medium. In this case, if the...
  2. Elbraido

    B Compressing Light: Reflection in Small Gaps

    Hi thereLet’s consider a photon of wavelength λ is being reflected across of gap d meters. The photon is a reflected back and forth between the same points on two horizontal sheets that reflect 100% of the light. What happens when the distance is smaller than wavelength? Thanks
  3. mgkii

    Frustrated Total Internal Reflection

    I've been reading into - and watching videos on - FTIR as an explanation of Quantum Tunnelling. The articles and videos I've watched switch between classical and quantum systems so frequently its left me with a question I can't find an answer to - the texts that seem like they might answer it...
  4. J

    Light Reflection and Particle Size

    I'm studying particle counters and one of the detection methods uses reflected light to determine the sizes of the particles. What principle does it base on? Thanks!
  5. V

    Second reflection angle of incidences in 3D

    Given Theta1(angle of incidence) and alpha1(azimuth angle). how do we obtain the second reflection angle theta3 and alpha3? Assuming the surface to be a mirror reflection(theta1 = theta2). Need an equation when varied the incident angles we would obtain the second reflection angles or a method...
  6. Kaushik

    Reflection of a wave by a rigid boundary

    I found this on the internet. Source How does the crest reach the end of the medium? As the other end is fixed there is no way the crest can reach the interface. Isn't it? My book gave an alternative explanation. It stated that as there is no net displacement at the interface, we can use the...
  7. C

    Acoustics type question on reflection....

    Hi, hopefully someone can help with showing me how I can work this one out as I am new to the topic area and a bit stumped. A piece of machinery is emitting a sound power level of 100 dB at 40 kHz. Calculate the level of the return signal after reflection from a wall 5 m away using the...
  8. E

    Huygen's Principle doesn't necessarily imply the law of reflection

    There are many diagrams like the following which demonstrate that if A acts as a point source of wavelets, then we will have constructive interference in the case that ##i=r## as shown, as we can show with a little geometry that the path difference is zero. However, surely this isn't the...
  9. theobromine

    Exploring Black & White Materials: Absorption vs. Reflection

    True black materials theoretically absorbs all wavelengths of visible light. True white materials reflect all wavelengths of light. If a material which was black at room temperature was heated up to incandescence so that it was emitting all visible wavelengths (white light), and then light was...
  10. D

    Optics: refraction and reflection

    Homework Statement: I have no idea how to start with this problem. I am trying to look for all the incident angles, refraction and reflection angles. And i don't know what the two radii are doing with y. Homework Equations: critical angle = arcsin (n2/n1) snell's law for refraction...
  11. F

    B Is it true that QED explains the reflection of light?

    About a month or two ago I posted this question in the "Classical Physics" forum: if the light doesn't interact with an electromagnetic field, then which force explains light reflection in a mirror? I didn't get a clear answer for that (besides advice to buy a book from Feynmann), so I went on...
  12. P

    Can a convex reflection be corrected using a concave mirror?

    If one took a photograph of a reflection from convex reflective surface. Could one use concave mirror to obtain the original undistorted image?
  13. D

    Thin film reflection of light

    Homework Statement: Light with wave length 648 nm in air is incident perpendicularly from air on a film 8.76 micrometers think and with refractive index 1.35. par of the light is reflected from the first surface of the film, and part enters the film and is reflected back at the second surface...
  14. XLAYZ

    Do the Fresnel equations of reflection apply to monochromatic light?

    Hello, I have a monochromatic light source (wavelength ~ 420 nm), which will be incident on the interface of two different media. Could someone please explain if the Fresnel equations applies with monochromatic light when estimating the reflectance and transmitance? Thank you in advance...
  15. F

    Which force is responsible for light's reflection in a surface?

    I think I understand how electromagnetic force works, so I predict that if I take a big, big, long flat table, charge that table with a big negative electric voltage (say -500kV), then I shoot an electron at that table at an angle, then the electron will be repulsed by the charge, will make a...
  16. P

    MHB Inverse Functions: Reflection of f(x) & g(x) Logic

    Can anyone explain the logic behind the answer? Taken from HiSet free practice test
  17. DaveC426913

    How does green screening technology handle secondary reflection of green?

    I get the basics of green screening. The processing software recognizes a small range of green and can substitute a different image where it occurs. Here's what I don't get: if a subject is standing in front of a green screen, they will have reflections of green. Notice that, in the...
  18. Manasan3010

    Reflection of a photon by an atom

    I suppose the reason I am able to see myself in mirror and not in wood is the reflection off a mirror is specular whereas wood is diffuse. In reflective material(e.g: silver) when the photon hits the frontline atom, the atom's electrons absorbs the energy and release it back with tiny energy...
  19. Neeraj

    Light Reflection Momentum - P=2Icos^2(A)/C

    Even if a beam of light strikes a reflective surface at an angle 'A', the change in momentum should be 2mc, P=2IcosA/C but I find it P= 2Icos^2(A)/C.
  20. N

    Is the ABCD matrix method suitable for a single reflection?

    I have a simple interface between vacuum and a uniaxial crystal. While it was easy to determine the reflection using Fresnel's equations, the analysis needs to be done "using matrices". We are only interested in the TE/TM reflections. Which method works best for this? ABCD/Ray transfer matrix...
  21. jason3w

    Create a focused beam angle of LED light using reflection

    Summary: Will an external surface reflect light into a more focused beam without using a traditional lens? Hey guys. Just trying to focus the light coming from a 1watt LED light source. It's native beam angle is 130 degrees. I'm hoping to focus it to around 30 degrees. We are creating an...
  22. S

    B Phase shift in Mach-Zehnder interferometer

    I'm confused by the phase shifts in a Mach-Zehnder interferometer because I keep finding two different explanations. One explanation (for example, given on Wikipedia, but also elsewhere) states that on each reflection, the phase shift is 180 degrees, but only, if light is reflected from the...
  23. F

    Derivation of the Optical Law of Reflection

    Problem Statement: Derive the optical law of reflection. Hint: Let light go from the point A (x1, y1) to B (x2, y,2) via an arbitrary point P = (x, 0) on a mirror along the x axis. Set dt/dx = (n/c) dD/dx = 0, where D = distance APB, and show that then theta = phi. Relevant Equations: t = nD/c...
  24. A

    I Which operator for reflection in quantum mechanics?

    Hello, I know we have the parity operator for inversion in quantum mechanics and for rotations we have the exponentials of the angular momentum/spin operators. But what if I want to write the operator that represent a reflection for example just switching y to -y, the matrix in real space...
  25. DPMF6973

    Index of refraction and wavelength

    The problem is multiple choice. A) refraction b) diffraction c) reflection d) dispersion An explanation would also be greatly appreciated!
  26. iVenky

    Reflection (intrinsic and characteristic impedance effects)

    Do we have reflection when the intrinsic impedance η=E/H between two media are matched but not necessarily the characteristic impedance (assuming a transmission line)? Basically, I have a case here shown below I have two parts with different geometries (this may not be a transmission-line, if...
  27. J

    Understanding Light Reflection: Exploring Photons and Reflective Surfaces

    Simple question. Are photons reflected as is from a surface like a mirror, or is the reflecting surface atoms capturing the photons and re-emitting them?
  28. Srihari05

    I Exploring Feynman's Theory on Reflection of Light from Glass Surfaces

    I recently started reading Feynmans book QED. There are a couple of questions I have regarding his theory on the percentage of light that is reflected of two surfaces of glass. My question is as follows, A piece of glass in fact has four surfaces. The front of the glass the back side of...
  29. A

    EM Wave Reflection and Refraction: Understanding the Fresnel Formalism

    For this question I want to clarify that 5k which is the electric field component perpendicular to the incident plane ( the xy plane) will be continuous for reflection and refraction , For which none of the options seems correct ,am I right?? The component of magnetic field perpendicular to...
  30. Beth N

    Thin-film interference: transmission & reflection of colors

    Homework Statement This is a 2 part question. I have a follow up question from the problem 1. A sheet of glass having an index of refraction of 1.40 is to be coated with a 187-nm thick film of material having a refractive index of 1.55 such that yellow light with a wavelength of 580nm (in...
  31. T

    How does the size between scatterers affect reflection?

    If a sound wave hits multiple scatterers spaced closer than the wavelength and moving fast but at different velocities how is the reflective beam is affected?
  32. C

    Is there refraction upon frustrated total internal reflection

    In frustrated total internal reflection, is there refraction corresponding to the refractive index difference between the first and third medium or does the light continue in straight line as it is usually depicted in graphic representations of the frustrated total internal reflection?
  33. Wrichik Basu

    Cause of polarisation due to reflection?

    Quoting Resnick and Halliday's Fundamentals of Physics (page 912) on polarization by reflection: It is also known that when light is incident at the interface at a particular angle θb, the Brewster angle, the reflected light is completely plane polarized. Why does light get polarized when it...
  34. ccdani

    Transmission of blue light through ceramics and surface roughness effects

    Hey :) I measured the transmission of blue visible light (350-550nm) through lithiumdisilicate ceramics with an ulbricht ball and an spectrometer. The light source was a led dental curing unit (bluephase style). The light guide was positioned direct on the ceramics. Now I wanted to test...
  35. Amaterasu21

    I SR Light Wavelength & Direction: Questions Explained

    Hi all, I have two questions about light in Special Relativity. (I'm going to pad these questions out with a few statements about my understanding of length contraction and time dilation, so you can see how I currently think about it and clear up any misconceptions if I've got the basic idea...
  36. N

    Optical Smoothest yet not specular metal or plastic sheets?

    I'll get into the details why I need this for below but first I'll explain what I'm looking for. I basically need a flat sheet of aluminum or any plastic in grey or black color that doesn't provide specular reflections, yet is smooth enough to not have any noticeable texture when looking with...
  37. S

    Reflection of only visible (safe) light on moon/mars

    I have seen many articles lately regarding planned manned missions to the moon and Mars but the question of radiation protection constantly comes up. Engineers keep proposing various shelter designs that use local materials (regolith) as a concrete base to absorb harmful radiation so that the...
  38. T

    Reflection Coefficent in Ultrasound scan

    Homework Statement Discuss the main advantage and disadvantage brought about by a reflection coefficient being very small, and hence highlight the attributes that an ultrasound scanner must have to fully exploit very small boundary reflection. Homework EquationsThe Attempt at a Solution I am...
  39. J

    Radar Cross section Vs Reflection Coefficient

    I am working on HFSS and designing Antennas for LOW RCS , in all previous works they calculate the S11 parameter for the unit cell then make an array form this unit cell and calculate the RCS , my question is what is the relation between S11 and RCS and why we calculate S11 for the unit...
  40. R

    Light Reflection: Understand How Light Interacts with Materials

    Hello, I have a question or perhaps a few questions regarding light and mirrors. When we point light at a mirror, it gets reflected back. But we can see the point light (assuming that it is a laser for the sake of simplicity) at a surface opposite to the reflective surface of the mirror. What...
  41. P

    I Diffuse Reflection: Calculating Momentum Transfer

    In a previous thread, we discussed specular reflection from a stationary and moving mirror, and argued that the momentum transfer was always normal to the mirrors surface. I became curious as if this was true in the case of diffuse reflection. But I'm not sure how to calculate that. It's...
  42. T

    What's the amount of energy lost in Total Internal Reflection?

    In Total Internal Reflection, the beam can still lose some energy as it reflects off the boundary of the medium it is within. This isn't covered under the Fresnel equations. The energy loss is probably lost in the form of evanescent waves. I tried searching for the formulae describing the...
  43. tanaygupta2000

    Does Phase Change on Reflection Violate Stokes Relation?

    We know that reflected light undergo a phase shift of π in EXTERNAL REFLECTION but there is no phase shift in INTERNAL REFLECTION . Does this violate Stokes Relation, which states that every reflected beam undergo of phase shift of π ?
  44. S

    Difference between emission due to absorption and reflection

    What is the difference between the photon interaction mechanisms in emission due to absorption and reflection?
  45. Biker

    Turning the refraction formula into reflection: Negative index

    In refraction of spherical surfaces, We derived the formula to be: ## u_2 L^{'} = u_1 L + (u_2 - u_1) R## Where ##L^{'}## is the reciprocal of the distance of the image. ##L## is the reciprocal of the distance of the object. ##u_2## is the refractive index of the medium that the light ray is...
  46. Georges

    Light Reflection: A 3D Designer's Guide

    Light is Reflected from the surface of the object or pass through it(interior) and then the light is reflected ? Sorry for my "noob" question i am a 3D designer just looking for some more knowledge Thanks in advance
  47. harambe

    I Optical reflection by metals

    https://eng.libretexts.org/Core/Materials_Science/Optical_Properties/Metallic_Reflection According to this article,metals are good reflectors at low frequencies.What about at high frequencies like visible or UV spectrum?Will this show deviation
  48. Muhammad Danish

    Reflection and Refraction formula help

    Homework Statement 2. Homework Equations 3. The Attempt at a Solution [/B] I tried to solve this question with the general formula n=sin i / sin r. 1.5 = sin 30/sin r, r = 19.4 = 19 which is option A. But option A is incorrect. Please guide me where am I wrong..
  49. bob012345

    Reflection from a small spherical mirror

    I was testing a small spherical mirror with sunlight and wondered about something. The size of the mirror is 2.5cm. The spot size of the reflected light grows over larger distances but it doesn't seem linear. For example, at a meter or less, the spot is very close to the mirror size but at a few...
  50. C

    How to work out the reflection point of waves

    Homework Statement When a workman strikes a steel pipeline with a hammer, he generates both longitudinal and transverse waves. The two types of reflected waves return 2.4 s apart. How far away is the reflection point? (For steel, vL = 6.2 km/s, vT = 3.2 km/s). Homework Equations Unknown...
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