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. J

    Incomplete destructive and constructive interference

    Homework Statement What are the values of incomplete destructive and constructive interference? Homework Equations The Attempt at a Solution when the path difference is in between 1 wavelength and 0.5 wavelength, there would be "incomplete" destructive interference. From my...
  2. J

    Can this classical double-slit experiment duplicate loss of interference?

    Not sure whether to put this in the QM forum or the classical forum, you'll see why-- I was thinking about the http://grad.physics.sunysb.edu/~amarch/ version of the double slit experiment, in which the information about which slit the particle went through is obtained in a somewhat unusual...
  3. T

    Mac Computer Electrical Interference

    I am trying to play a movie from my macbook pro with the video to a standard HD tv and the audio to a guitar amplifier. I connected the guitar amplifier to my macbook pro through a 1/4" to headphone jack cable and the sound outputted to the amp was fine, just as I wanted it. As soon as I...
  4. O

    Wave interference and superposition

    hi everyone, i was wondering whether i can change this sentence ( if the phase difference changes rapidly , the average effect of no interference is recorded.) to( if the phase difference changes rapidly , the average effect of no superposition is recorded.) as i remember that the term...
  5. ezfzx

    Thin Film Interference: The Movie

    I put together this little movie as (hopefully) the first in a series. http://www.youtube.com/watch?v=xjMjWtntm9k" My target audience is a second semester class of physics students that have already had a lectures in basic wave optics. When I give this URL to my students, it's with the...
  6. M

    Three problems concerning light interference and snells

    5. Two slits are separated by 0.195 mm. An interference pattern is formed on a screen 33.0 cm away by 656.3-nm light. Calculate the fraction of the maximum intensity a distance 0.600 cm away from the central maximum. d =.000195m L = .33 m lambda = 656.3 nm y = .006m it's a small angle...
  7. O

    About wave interference

    hey guys, for condtion of observable interference, why do the path difference should be smaller than the coherent length ?? thx
  8. S

    Constructive/Destructive Interference of Two Glass Plates

    Homework Statement "Light is incident from above two plates of glass separated on both ends by small wires of diameter d = .6um. Considering only interference between light reflected from the bottom surface of the upper plate and light reflected from the upper surface of the lower plate...
  9. P

    What Happens to the Photons in Destructive Interference?

    I know about the law of conservation of energy, and I understand interference effects conceptually, but when I put the two together I'm a little confused. I know that the energy of light must simply by transformed in destructive interference...but where does it go and how? If the...
  10. N

    Thin-film interference problem

    Homework Statement Light of wavelength 470 nm passes through a block of material with a refractive index n = 1.30, some of it is reflected off the air-block boundary and some of it is transmitted through air (n=1.00) with thickness t, and is then reflected off another block also with n = 1.30...
  11. J

    Interference between the particles

    Hi, I am new to QM and really confused with some concepts. Assume two alpha particles come out from two different sources and reach the same detector, so the probability to detect some particles should be |f+g|^2 (f, g are the amplitude of 1st and 2nd alpha particle, respectively). If they are...
  12. J

    Solving Wave Interference: A Study of Frequency & Amplitude

    Homework Statement Write a wave in one space dimension as ARe(ei(kx-wt-d))where A is the amplitude of the wave. Find a second wave of the same frequency such that the sum of the two vanishes at x = 0 and x = L. Assuming the wave velocity c = w/|k| is fixed, for what frequencies ! is this...
  13. S

    Energy conservation in destructive interference.

    I have followed some of the previous posts on the topic , but the conflicting arguments have left more than confused. Consider this simple scenario : Two wave pulses on a string generated by identical sources but with a phase difference of 180 degrees meet and interfere destructively. For...
  14. M

    Sound Waves and Interference Problem - Check My Work?

    Okay, I have this problem worked out, but I have no clue if my answers are right. Could someone please check my work and give me some confidence or show me where I may have messed up. Homework Statement Two loudspeakers, one of them generates sound with 400 W power the other with 100 W. The...
  15. E

    Wave Interference with 2 speakers

    Homework Statement Two speakers located 4.0 m apart. Listener is seated 25.0m from 1 speaker, and 27.0m from the other. We drive the two speakers at a freq. which we sweep from 100 to 500 Hz. If the 2 speakers are in phase, find the frequencies at which the waves constructively/destructively...
  16. T

    Optimizing 4-slit Interference Pattern for θ1st Min with Homework Solution

    Homework Statement A 4-slit interference pattern is created by 4 slits spaced 2μm apart. At what approximate angle θ does the intensity go to zero the first time, if the incoming light has a wavelength of 450 nm? θ1st min = Homework Equations d*sinθ = m\lambda The Attempt at a...
  17. T

    What Causes Radio Stations to Mix and How Does it Affect Listening?

    What does it mean physically when radio stations mix? As in if you are listening to one station, but you begin to here another and eventually only here the wrong station.
  18. P

    Calculate Max Wavelength of Sound Emitted by Loudspeakers

    Hi, Two loudspeakers are connected to the same audio oscillator. An observer walks in between them. At a point M, halfway between the speakers he hears a loud sound. By the time he gets to a point P 2m away from M he hears no sound at all. Calculate the maximum wavelength of sound emitted by...
  19. F

    Wave nature of electron, interference and standing waves

    Hello, was wondering a couple of details on the wave nature of electrons and the state of the art in this field. In particular: Is it practical and possible (easily) to create a cm sized electron interference pattern (fringes are in the cm size magnitude). I have so far seen Low Energy...
  20. R

    Light wave interference questions

    I have two questions concerning what happens when light interference occurs. In destructive interference of coherent light beams, how is energy conserved, both when interference occurs in air and in a vacuum. When non coherent light beams intersect is space there is no interference...
  21. M

    What is the difference between superposition and interference?

    Hello In my textbook There are two headlines "Superposition" and "interference but I can't recognize any difference between the two terms So what is the difference between them? Thanks
  22. D

    3 phase 4 wire conductors radiated electromagnetic interference?

    If you have a 3 phase 4 wire distribution where the 3 phase conductors and 1 neutral is inside a pvc conduit, how would you model the force of the electromagnetic field at a certain distance away from the conduit? Assuming the loads are balanced, the currents would sum to zero on the...
  23. P

    Calculate Lowest Frequency for X&Y: Constructive/Destructive Interference at Q

    Hi, Question: X and Y are two identical sources of sound which emit in phase. Calculate the lowest possible value of frequency of the sources for there to be (a) constructive (b) destructive interference at Q. So, X is at 1.8 m from Q and Y is 1.2 m away from Q. a) If they leave in...
  24. S

    Analyzing wave interference patterns

    Hello, this is my first visit to PF. I have a question that I can tell isn't very difficult, but I can't seem get my head around it, maybe i just need to review my text and make an attempt tomorrow. Homework Statement Consider the point P in the following diagram. Analyze this diagram to show...
  25. C

    EM Destructive interference of two coherent beams

    Suppose you have two coherent microwave beams, one beam at 45 degrees to a reflecting wall and the other one at 90 degrees, with the two beams pointing to the same point on the wall. If the two beams are 180 degrees out of phase and destructively interfere at the point on the wall, will the...
  26. J

    Quantum Interference in tunneling electron transport?

    Can anyone break down "quantum interference" in the tunneling transport through aromatic organic molecules? The Math is a little fuzzy, but with a few seminal reference or a conceptual description i might be able to wrap my mind lips around this knowledge pop! haha. any help would be appreciated.
  27. K

    An exercise about thin-film interference

    Homework Statement We have a thin film of glass which has thickness t=\lambda and n=1.5 and light (\lambda) passing through it with an angle \theta_0. We have to find the minimum angle that allows us to see both constructive and destructive interference. Homework Equations Max...
  28. I

    Help me understand interference and diffraction better

    Homework Statement I've been reading a book about waves. I skipped the test earlier this year because I had not done any problems and thought it would be a waste of time to try. But now I kind of have to do it, I've re-read the book but it's much to understand and remember. Especially the...
  29. K

    Geometrical problem related to thin film interference

    Look at the picture below, I have to prove that the optical path length difference is \Delta=n(BC+CD)-BE=2nd\cos(r) [PLAIN]http://img200.imageshack.us/img200/2271/schermata082455775alle1.th.png The problem is just how to get 2nd\cos(r) I actually don't have any idea :\ I have...
  30. K

    Thin film interference formulae

    Hello, I am trying to understand thin film (in air) interference but I have a problem: I know we have destructive interference when \delta=(2m+1)\pi. Now i can try to calculate the thickness of the film to get it, so since \delta =\frac{4nt\pi}{\lambda} - \pi where t is the thickness...
  31. P

    How Do Antenna Positions Affect Radio Wave Interference?

    Two radio antennas A and B radiate in phase. Antenna B is a distance of 130 m to the right of antenna A. Consider point Q along the extension of the line connecting the antennas, a horizontal distance of 50.0 m to the right of antenna B. The frequency, and hence the wavelength, of the emitted...
  32. T

    Calculating Ym and R for Two-Slit Interference: Tips and Tricks"

    Right so I've been stuck with this for a while now and I'm sure it's just something simple that I've missed. Right so the question says there are a pair of closely spaced slits (0.300mm apart). By changing the spacing the bright fringe moves from position m=2 to m=3. The wavelength remains...
  33. G

    Where does the waves energy go when destructive interference occurs?

    For example, when two light waves completely cancel each other out, there is the black on an interference pattern, indicating absence of light. What happens to the photons? It seems they cease to exist. Also, How does this relate (or not) to the "Conservation of Energy" law? Any...
  34. P

    Finding Constructive Interference

    Homework Statement A college student is at a concert and really wants to hear the music, so she sits between two in-phase loudspeakers, which point toward each other and are 53.2 m apart. The speakers emit sound at a frequency of 459 Hz. At the midpoint between the speakers, there will be...
  35. I

    Interference between different kinds of particles

    I have only an completed one course on quantum mechanics so please excuse me if this seems rudimentary. In my course we only dealt with electrons and their interference with one another. Is it possible for an electron and a proton to interfere with one another? Or more generally, can...
  36. zimo

    Interference (Young's experiment) and an adhesive tape

    Homework Statement At a young's experiment arrangement, there is a 500nm light beam, a distance of 1m from the slits to the screen and a 0.25mm between the two slits In what way the interference pattern will change if an adhesive tape is being taped to one of the slits with a 1mm thickness and...
  37. L

    The interference term. Confused.

    Can someone explain what the difference is between the expectation value of an observable in a pure vs a mixed state. The equations are identical. For example with spin up and down |A|^2<S_u|O|S_u> + |B|^2<S_d|O|S_d>
  38. M

    Single photon interference time threshold (double slit experiment)

    In the paper (AIP Conf. Proc. 810 (2006), 360): Mardari outlines three predictions of quantum self-interference, all of which empirical evidence is presented that appear to refute all three. The implications of the paper is interesting but of these I am particularly interested in the...
  39. N

    Interference Pattern in Cascaded Experiments

    "consider the same interference experiment,the interference pattern produced is used to illuminate the next source in series,which then produces a new interference pattern,this gets cascaded say 10 times and the final interference pattern is obtained on the wall. now ,the observer, observing...
  40. K

    Double-Slit Interference (Thank you in Advance)

    Homework Statement A beam of electrons is accelerated from rest and then passes through a pair of identical thin slits that are 2 nm apart. You observe the first double-slit interference dark fringes occurring at ±20◦ from the original direction of the beam when viewed on a distant screen. (A)...
  41. B

    Constructive Wave Interference: Can Two Waves Combine?

    Hi, I was wondering if two waves, whom both have the same frequency and wave, could be combined together in a constructive interference way, even if they did not have the same amplitude?
  42. K

    Water tank and wave interference question?

    Homework Statement In a large water tank experiment, water waves are generated with straight, parallel wave fronts, 3.0m apart. The wave fronts pass through two openings 5.0m apart in a long board. The end of the tank is 3.0m beyond the board. Where should you stand, relative to the...
  43. S

    In DCQE you can get which way and still get interference?

    in DCQE you can get which way and still get interference? for example when the s-photon strikes the detector ...let's assume setup is such that which-way is known now we send the idler via erasure (after registration of s) and later when we sub-sample via co-incidence counting we get...
  44. V

    Interference pattern after the region of the interference

    Hi, I'm concerned about one question about light interference. It's said that light energy is redistributed during interference. That creates pattern. One slit or double slit interference create maximums and minimums on the screen where the interference takes place. Now imagine a...
  45. zonde

    Where does photon interference happen

    If we look at http://en.wikipedia.org/wiki/Mach%E2%80%93Zehnder_interferometer" I think it's fair to say that any interpretation of QM says that there are appear no photons (in idealized case) at detector 2 as there are no detections. Basically that means that photon interference takes place at...
  46. Mueiz

    Electromagnetic Interference in Einestien Field Equation

    According to EM theory,in the absence of any interaction with matter, destructive interference in one location will always be balanced by constructive interference in another location keeping the law of conservation which means that there is no local conservation law for energy flux regarding...
  47. S

    Single particle Interference – Photon Vs Electron Vs Buckyball

    Is the mechanism behind the single particle interference between photon, electron and buckyball different? Reason for interference Photon - interference caused by maxwell electromagnetic waves? Electron - interference caused by Schroedinger probability waves? Buckyball - interference...
  48. S

    Co-relation between interference and polarization

    Let's say we send two photons at same time through double slit: Would interference pattern form if: 1. Both the photons are of different polarization? (i.e. one left polarized and the other right) 2. Both the photons are of same polarization?
  49. M

    Difference Between Interference and Diffraction

    Can anyone tell me the difference between interference in double slit's and single slit diffraction?
  50. D

    Interference of fibre optic signals with mobile phones' microwaves?

    I got an SMS educating people how to find out the presence of a hidden cam in a trial room of a textile showroom or bathroom. It goes like this :- "If you can't make a call in the room,the there is a hidden cam. This is due to the interference of the fibre optic with the signal transfer."...
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