What is Interference: Definition and 999 Discussions

In physics, interference is a phenomenon in which two waves superpose to form a resultant wave of greater, lower, or the same amplitude. Constructive and destructive interference result from the interaction of waves that are correlated or coherent with each other, either because they come from the same source or because they have the same or nearly the same frequency. Interference effects can be observed with all types of waves, for example, light, radio, acoustic, surface water waves, gravity waves, or matter waves. The resulting images or graphs are called interferograms.

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  1. T

    I Trying to understand the interference limits of matter-wave

    Given the de Broile wave matter equation, wavelength = plank's constant / momentum,... 1) what's the maximum distance from the electron until its wave like behaviour stops interfering with its surroundings? 2) why the bigger the wavelength, the more the electron is to interact with its...
  2. ThunderLight

    Orthogonal Polarisation in EM waves and Interference

    I've been trying to get my head around Polarisation and how it achieves orthogonality. I'm not sure if this should be in Physics or Electrical Engineering Section. (Mods can move this where appropriate) I know that 2 EM wave with linear polarisations where one wave is shifted by π, they would...
  3. J

    B Measuring velocity and interference?

    If I measured the velocity of an electron what happens to its position? Does it collapse into a specific position or is it still uncertain? Here's a thought experiment... we measure the velocity of an electron and then send it through the double slit at the same time. Does the electron still...
  4. F

    Thin film interference - why thin, exactly?

    Hi, in every explanation of thin film interference I came across, little or nothing is said as to why the layer of transparent material creating the effect should be thin. What would go wrong if that is not the case? I'm asking because it seems to me that, in principle, the mathematic...
  5. Daniel Petka

    Can destructive interference cause energy loss and how can it be regained?

    This is a really silly question and its bugging me. Do I lose energy through destructive interference? If not... then how can I get back what I invested before? Thanks, hope I understand the waves soon :)
  6. Nikhil N

    EMI(Electro Magnetic Interference) Magnitude and Frequency

    I want to analyze the efficiency of my data communication between slaves and master in the presence of interference. The protocol what I am using is modbus, with baud rate of 9600 , I am using 1000 ft cable. What I am struggling to do is, how to couple the noise into the cable in a way it is...
  7. Z

    I How Fermat's principle interprets diffraction and interference

    <Moved from the homework section> 1. Homework Statement I have read several chapters of De Brogile's article "the theory of quanta".The motion of a particle could be analogious to a ray in general optics.This is an analogy between Maupertui's principle and fermat's principle. How to use this...
  8. N

    B Interference pattern after a particle is detected?

    Say we have a particle, like an electron in a double slit experiment. And say that we have a measuring apparatus to detect it right after its fired out of the electron gun. And after that it goes through the double slit and hits the detector plate. Would we see an interference pattern? If the...
  9. T

    Finding the Distance Between Sound and Wave Maxima at a Train Station

    Homework Statement Two trains approach the train station from opposite sides each moving at an initialvelocity of 120 km/h with respect to the station and slowing down to a halt in 20seconds. If both trains are whistling at 5000 Hz, find the distance between the zeroand first order maxima as a...
  10. A

    Answer: Neutron Interference: Understanding Kinetic Energy

    Homework Statement the question details are given in the attachment Homework Equations momentum = √2mE where m is mass of neutron and E is its kinetic energy The Attempt at a Solution initially i accounted for the energy change during the path followed by the neutron but later i got...
  11. P

    What happens to intensity during light interference?

    Dear Every Smart Person, I am not a scientist or a physicist by any means, but I have a concept that has been literally driving me crazy all day. No matter how much I read, I can't make sense of it. Here it goes. I work in the LED Lighting space. In that space, there are two types of LEDs: a...
  12. L

    3 Examples of jobs related to the interference of light

    Homework Statement Find 3 careers that are in some way related to the interference of light. Give a brief description of each career. Homework EquationsThe Attempt at a Solution My examples are X-ray Technician, Photonics Engineering and Optical Physics. My question is, is optical...
  13. N

    I How does MWI deal with the destruction of interference?

    How does MWI deal with the destruction of interference in the double slit experiment when a detector is placed at the slits? Since the wave function never collapses, and the universe doesn't actually split in MWI, how does the interference go away? Does the measuring device at the slits reshape...
  14. Vanessa Avila

    Light (Constructive/Destructive Interference)

    Homework Statement This is not a homework question but I would like if someone could explain to me when to consider what equation constructive/destructive? I learned these two equations very vaguely in class: dsinθ = mλ or d(ym)/L=mλ dsinθ = (m+1/2)λ or d(ym)/L = (m+1/2)λ The power point...
  15. M

    B Interference pattern, one particle at a time

    [Mentor's note: Split off from another thread because it's a different question] I have a question about the single-photon double-slit experiment's results that isn't about the role of consciousness. Should I go ahead and ask it here or ask it elsewhere? (Briefly: If the results are lots of...
  16. B

    Determination of Ca/Mg in orthophosphate-rich solutions

    I want to measure the Ca and Mg concentration in a solution that contains up to 250 mg/L of PO43-. Apparently, orthophosphates interfere with both flame photometric methods and complexometric methods with EDTA (or so I've read). Is there a standard method for measuring Ca and Mg in this type of...
  17. H

    Where to Stand in a Water Tank Experiment to Experience Minimal Wave Action?

    Homework Statement In a large water tank experiment, water waves are generated with straight, parallel wave fronts, 3.00 m apart. The wave fronts pass through two openings 5.00 m apart in a long board. The end of the tank is 3.00 m beyond the board. Where would you stand, relative to the...
  18. CricK0es

    Interference from coherent light sources

    Homework Statement Four equally spaced coherent light sources (n=4) with a wavelength of 500nm are separated by a distance d = 0.1mm. The interference pattern is viewed on a screen at a distance of 1.4m. Find the positions of the principle interference maxima and compare their width with that...
  19. R

    Out of phase light/photons, would it be measurable?

    With sound you can create out of phase signals and they cancel out, this is not possible with light as it does not interact like sound does. If it was possible to create two light sources in that were exactly 180 degrees out of phase with each other and aim them at a common point (eg an...
  20. D

    Determining hole size using laser interference

    Homework Statement Lisa makes a hole in aluminum foil. She wants to know the diameter of the hole. She points a laser through the hole. That picture is what appears on the wall that is 1,25 meters behind the aluminum. the distance between every circle is 8mm. the wave length is 633nm...
  21. G

    I What destroys interference: Possibility or actual measurment?

    Hi. If we place two perpendicularly oriented linear polarizers at a double slit, there will be no interference pattern. In the wave picture, this is trivial: Two waves with perpendicular polarization cannot interfere. In a quantum picture, I've often seen the interpretation that the sheer...
  22. Cocoleia

    Thin film interference and external / internal reflection

    Homework Statement I am working on a thin film interference problem where i have to find the phase difference. What is the relationship between external/internal reflection and the thin film interferenceHomework Equations for external: [/B] for internal: The Attempt at a Solution So far i...
  23. B

    Synchronous Sources and Interference

    Hi, What is the scientific definition of "synchronous sources" when we talk about the conditions of interference? Thank you.
  24. C

    About interference, momentum and thrust....

    [Mentors' note - this post has been edited to remove some discussion of the EM-drive. See https://www.physicsforums.com/threads/nasas-em-drive.884753/ for our current policy with regard to em-drive discussions] Hello. Imagine a closed box with reflecting walls. Inside you have two antennas...
  25. W

    Question on destructive and constructive interference

    Homework Statement Two speakers A and B are 3.50m apart and each one is emitting a frequency of 444Hz. However because of signal delays, speaker A is 1/4 of a period ahead of B. Find all points relative to the centerline between A and B where there is constructive interference. Include angles...
  26. nso09

    Relationship of slit, wavelength, and intensity

    Homework Statement Coherent electromagnetic radiation is sent through a slit of width 0.01 mm. For which of the following wavelengths will there be no points in the diffraction pattern where the intensity is zero? A. Blue light of wavelength ##\lambda=500 nm## B. Infrared light of wavelength...
  27. Biker

    Constructive and destructive interference

    Homework Statement Suppose you have two pulses, One is a trough, It's amplitude is 3 cm and the other is a crest and its amplitude is 9 cm. Assuming they have the same wave length when they overlap the energy of the created wave is: 1- 1/16 E 2- 1/4 E 3- E 4- 4E Homework Equations ##E## is...
  28. nso09

    Interference on a mirror -- waves confusion

    Homework Statement ##d=0.52 cm,## ##\lambda=431nm##, ##L=119 m## Homework Equations ##dsin\theta=(m+1/2)\lambda## for constructive/bright fringes since there is a pi shift already The Attempt at a Solution a) $$sin\theta\leq1$$ $$(.0052/431e-9)-0.5=m=12064$$ 2 \e{3} $$ total bright fringes =...
  29. Hamal_Arietis

    Light Interference: Find Condition of d for Constructive Interference

    Homework Statement [/B] Find condition of d that constructive interference occurs with m=1,2,3,... a)##(m-\frac{1}{2})\frac{\lambda}{2}## b)##m\frac{\lambda}{2}## c)##(m-\frac{1}{2})\lambda## d)##m\lambda## Homework Equations optical path difference (OPD) must equal ##m\lambda## The Attempt at...
  30. S

    Thickness of film for maximum interference

    Homework Statement As shown in the figure below, beams of light whose wavelength in air is 600 nm are perpendicularly incident upon two transparent thin films (A and B) in the same phase. The thickness of A and B is l. The refractive indices of A and B are, respectively, nA and nB. The...
  31. K

    Automotive How to optimize an interference fit for a sheet metal ring

    Hi, I am new to this forum. I need to design an interference fit for a 1.5 mm thick SS ring. The interference fit is between this ring and another 1.5 mm thick SS sheet metal can without any groove. The ring is bent outwards at a specific angle.(please refer attached image) We know amount of...
  32. NatanijelVasic

    Unraveling the Mystery of Binaural Beats: Nat's Story

    Hello everyone, I have been thinking about binaural beats, and after learning about the inner workings of the ear, there is something that I cannot explain. A binaural beat is the pulsating effect perceived by the brain when slightly offset frequencies are played in each ear. In my example...
  33. S

    B Interferometry on photodetector

    Hello! I am trying an interferometry experiment using the Michelson Morley experiment. I managed to obtain the interference pattern on a screen, but I want to use an photodetector and I am not sure what should I obtain. As I know, the oscilloscope shows the intensity of the light, so if I modify...
  34. Chris Frisella

    Does Destructive Interference Cancel Energy?

    Does it cancel it, or just create an equilibrium of forces upon a point(s)? Example: If you had a string and you sent a wave down one end, and the opposite wave from the other, once they meet there will be an instant when the string is flat as if there had never been waves introduced. But, if...
  35. E

    I Quantum superposition from interference?

    While studying the wiki article for Quantum Superposition, I find this sentence: “An example of a physically observable manifestation of superposition is interference peaks from an electron wave in a double-slit experiment.” Can someone explain how interference proves (shows? demonstrates?)...
  36. E

    Hair/wire laser diffraction interference pattern

    Hair/wire laser diffraction interference pattern - does it follow single-slit or double-slit? for single-slit interference, the equation nλ = d (y/D), (d is the width of the single-slit, y is the distance between central BRIGHT fringe to the nth DARK fringe, D is the distance from slit to...
  37. G

    Is there such thing as magnetic interference?

    Say I place a magnet on a table, and I have a metal in close proximity. Will its magnetic field change due to the presence of this metal, however minute? What if I had another magnet or the table itself is made of materials the magnet is slightly attracted to? Does this phenomenon even exist?
  38. andrewkirk

    Acoustic 'beats' from mismatched musical frequencies - Comments

    andrewkirk submitted a new PF Insights post Acoustic 'beats' from mismatched musical frequencies Continue reading the Original PF Insights Post.
  39. T

    How do different path differences affect interference in sound waves?

    Homework Statement Two loudspeakers, A and B, are driven by the same amplifier and emit sinusoidal waves in phase. Speaker B is L = 2.00 m to the right of speaker A. The frequency of the sound waves produced by the loudspeakers is f = 206 Hz. Consider point P between the speakers and along the...
  40. D

    Why do sound waves with slightly different frequencies create beats?

    I have a question about 'beats' between two sound waves of slightly different frequencies. Basically, I think I understand everything on this page (and have read a few textbooks on this): http://www.animations.physics.unsw.edu.au/jw/beats.htm . And in practice, I work with this concept all the...
  41. Quantum of Solace

    B Destructive interference and conservation of momentum

    If two photons traveling in the same direction but out of phase cancel each other out, what happens to the energy and momentum?
  42. nomadreid

    What does GPS do about atmospheric interference?

    Although microwaves are not refracted much in the atmosphere, there is some, and the atmosphere does vary a lot, and the GPS depends on a pretty exact timing of the signals between ground to satellite. So how do GPS systems take the atmospheric refraction into consideration?
  43. S

    Device that detect waves in a frequency range and beats

    Homework Statement You have a device that can measure sound waves only if the frequency of the wave is in the range ##0.8 kHz- 20 kHz##. You have a whistle that produces sound waves at ##21.5kHz##. You ride a bike moving away from a wall, at the same time you blow the whistle and hold the...
  44. S

    Beats: frequency of resulting wave vs. beats frequency

    The beats frequency heard from the interference of two sound waves with frequencies ##f_1## and ##f_2## is $$\nu=|f_1-f_2|$$ Nevertheless the frequency of the resulting wave is not ##\nu## but the mean value of the two frequencies $$f_{resulting}=\frac{f_1+f_2}{2}$$ As far as I understood...
  45. EmilyBergendahl

    Interference in Thin Films: Grade 12 Optics Review

    Homework Statement Would you see the same thin film interference pattern in a film of soap surrounded by air and a film of soap on glass? Why or why not? Homework Equations None The Attempt at a Solution Yes, you would see the same thin film interference pattern in a film of soap surrounded...
  46. EmilyBergendahl

    Double Slit: Separation and Path Length

    Homework Statement A double slit apparatus is held 1.2 m from a screen. (a) When red light (λ = 600 nm) is sent through the double slit, the interference pattern on the screen shows a distance of 12.5 cm between the first and tenth dark fringes. What is the separation of the slits? (b) What...
  47. EmilyBergendahl

    What is the Explanation for the Interference Pattern in Thin Soap Films?

    Homework Statement Green light is shone onto two soap films. An observer looking down at the soap films sees that soap film X appears uniformly green while soap film Y has green and black bands. If air is the medium on either side of the soap film, the best explanation of this pattern is...
  48. S

    I Spatial interference fringes in Hong-Ou-Mandel

    If we can slightly skew the optics in a HOM setup, so that the phase difference between Beam-1 and Beam-2 varies slowly across one of the detection planes, then would we see dark and bright regions in the cumulative pattern (assuming an array type i.e. spatially resolved detector) ??
  49. Chevreuil

    Mount Rack & Pinion Interference in PTC Creo | Avoidance & Solutions

    Hello, I have downloaded CAD models of a rack and pinion, and I don't seem to be able to mount them up in PTC Creo without quite obvious interference. The pinion has a pitch diameter of 24 mm, and a modulus 2. The "pitch diameter" of the rack is exactly one modulus lower than the tip of the...
  50. E

    B Time Dilation Model & Wave Interference: Newbie Questions Answered

    I have some newbie kind of confusion The model in question is taken from wikipedia: and If, in the first model, the light ray is reflected back to its source, could there be some kind of detectable interference at the midpoint (where the blue arrows are)? If the answer is yes, would this...
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