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. A

    Can Beats Be Heard When Tuning a Guitar Using the Beat Method?

    I'm studying wave interference and I have a few questions regarding it that I can't quite figure out: 1.) I was once taught that for waves to interfere, they have to be of the same frequency, but then how can beat interference occur? What are the actual requirements for interference? 2.)...
  2. C

    How can you prepare a state with a single photon?

    I'm trying to write up an experiment that I have done on single photon interference. The design is as follows: Class 2 HeNe laser 25 micron pinhole double slit output via CCD I have all the data, but I cannot find anything that says that having a small pinhole about 80cm from the double slit...
  3. P

    Explaining the Rainbow Colors in Thin Films: Interference Homework Problem

    Homework Statement When light is shined on thin films the interference pattern results in: a. there is no interference pattern *b. rainbow like colors c. light and dark pattern with no separation of colors d. a mirror quality reflection e. polarization of the light The...
  4. K

    How Far Do Light Interference Patterns Extend in Space?

    Say you have two points that are close to each other emitting light in phase with each other, such as in the diagram below Will the interference pattern that results occur all throughout space (all along x and y and z directions), or is there some distance from the points after which there...
  5. X

    Destructive interference in the wavefunction, is this conceptually explainable?

    Hello, destructive interference seems like an important part of quantum physics, but I'm finding it very hard to grasp it conceptually. For instance in the Elitzur–Vaidman bomb tester, destructive interference in the mirror is used to determine if one of the paths is blocked. What exactly is...
  6. F

    Determining phase of resultant from partial interference of waves

    When you have waves that are out of phase by some fraction of a cycle, e.g not exactly in phase and not exactly 180 degrees anti-phase, how do you determine the phase (relative to the original component waveforms) of the resultant? Specifically, is there an equation that solves for phase...
  7. Z

    Problem interpreting this interference question

    1. Homework Statement "A thin piece of metal foil of thickness 0.0700mm separates one end of two pieces of optically flat glass. The top sheet is 12.0cm long. Light of wavelength 529nm is normally incident on the glass. How many interference fringes are observed per cm in the reflected...
  8. D

    Interference terms in particle spin

    In the double slit experiment there are interference terms which are responsible for the way in which particles appear on a screen (diffraction pattern). The density matrix for an electron with spin |+X> going into a stern Gerlach alligned in the z direction also has off diagonal terms which...
  9. P

    Does Energy Redistribution in Wave Interference Happen Superluminally?

    Because energy cannot be destroyed, when waves interfere destructively the energy doesn't really disappear, it's simply redistributed to areas of constructive interference, right? But isn't this energy redistribution instantaneous?
  10. Y

    Understanding the Scully and Yoon-Ho Experiment: Interference in D0

    Hi, I wanted to ask a question regarding the D0 detector in the original Scully and Yoon-Ho experiment (from 2000): According to the paper itself, and to the wiki article: "Note that the total pattern of all signal photons at D0, whose entangled idlers went to multiple different...
  11. C

    Calculating Wavelength from Double-Slit Interference Pattern

    Homework Statement A double-slit interference pattern is created by two narrow slits spaced 0.21mm apart. The distance between the first and the fifth minimum on a screen 60cm behind the slits is 6.2mm. What is the wavelength of the light used in this experiment? Homework Equations...
  12. S

    Do we really need physical/real waves to explain single particle interference?

    in explaining the interference pattern that happens in double slit, single particle interference - some of the interpretations, for example De Broglie–Bohm interpretation: assumes that (some sort of) "waves" travel through both slits simultaneously and interfere with each other the...
  13. A

    Why need a screen to display interference

    Homework Statement why do we need a viewing screen in order to see interference patterns? why can we see interference patterns through our fingers when we look at a distant light source and we don't need a screen in that case? what do we mean by visible light? can we see the wave itself...
  14. QuarkCharmer

    Wave Interference concept help

    Homework Statement Homework Equations y_{3} = y_{1}+y_{2} f(x,t) = y_{m}sin(kx-ωt+\phi) The Attempt at a Solution So, I'm going back over a proof done in my physics course, where the sum of two waves equals the resulting wave. The proof was on constructive and destructive interference. I'm...
  15. S

    Need a demonstration of interference in Waves

    Hey, I am having a project in Physics, and the project is about interference in Waves. We got a task, and I need to demonstrate how waves interfere with each other. I got a demonstration with Lasers, how they split up, but I also need a much more simple demonstration. Something like when...
  16. J

    Destructive interference in electron diffraction

    Whatt happens during destructive interference of electrons. Two electrons(waves) combine and cancel each other out so no dot is produced on the screen?? Then where did the electrons go? First of all : How is a dot created on the screen? - is it because of the wave nature of electron or...
  17. S

    How is interference by longer path generally explained by physicists?

    The interference of light (or single particle photon) is as if the photon traveled all possible paths. now the something ("wave") traveling the longer path would arrive late and hence cannot interfere (timing issue). Yet the pattern shows interference. Some conclude that the past and...
  18. S

    Standing wave interference patterns on liquid metals

    Hi, first post, so take it easy on me, I've had an idea for producing metallic objects with high surface area for several years, but lack the necessary physics knowledge to act on it or, really, inclination (and money) to go through years of school to gain such. The idea is as follows: A...
  19. F

    Understanding Interference: Wave A & Wave B

    Interference Question: I'm trying to understand interference, I get the basic concept, that when two EM waves are superposed the resultant's amplitude of the vector sum of each original wave's respective amplitude. It's the following the creates confusion. Picture the figure below. Wave A...
  20. C

    Double Slit Wave Interference Question

    Homework Statement Blue light (λ = 482 nm) is directed through parallel slits separated by 0.15 mm. A fringe pattern appears on a ascreen 2.00 m away. How far from the central axis on either side are the second order dark bands? λ = 4.82 x 10-7 m d = 1.5 x10-4 m L = 2.00 m m = 2 y= ...
  21. F

    Interference: Calculating the direction of the resultant wave

    Two coherent waveforms (could be pulses or wavetrains), that intersect at an angle, as in the picture below. Assume that we are able to make the waveforms in phase and superposed at the point of intersection, such that they constructively interfere. In what direction does the...
  22. P

    Thermal expansion of an interference fit

    I have a bearing that is fixed into its housing by means of an interference fit (to test the effects of having a bearing that has become stuck due to build up of contaminants). I am using a bearing of ID 15.92mm ± 0.005 made of High lead Tin Bronze Alloy with a thermal coefficient of expansion...
  23. A

    Interference Pattern versus SR

    I posted this thought experiment in a previous thread before 4 months or so, but I would like to reiterate it now: A frame of reference (FOR) has double slits moves relative to a ground FOR. Let`s make an arrangement so that when the 2 ends of FORs coincide, 2 small slits of moving FOR are...
  24. S

    Single slit single particle interference

    If we send one photon, at a time, through a single slit do we observe the interference pattern? Specially at the edges
  25. A

    Diffraction and interference presentation

    Homework Statement hi, my problem isn't exactly mathematical. I am currently making a presentation on diffraction and interference and its asked me to make overheads containing main concept, scientific and theoretical background and other topics im confused on the difference between the...
  26. M

    Breaking EM Destructive Interference

    Hi, I have a question about destructive interference. Suppose I have two very closely spaced EM sources, e.g two RF emitters. At a point far away from the sources the arbitrarily orientated magnetic field due to source one is: B1(t)=sin(ωt) and source two: B2(t)=sin(ωt+pi) so the total field...
  27. A

    Interference fringe of light beams of different frequencies

    I have a question. If you have two light beams of different frequencies, would you observe interference fringes?
  28. S

    Interference in Air Wedges exercise

    I have this question for my physics assignment. Homework Statement Two plane glass plates 10.0 cm long, touching at one end , are separated at the other end by strip of paper 1.5x10^{-3} mm thick. When the plates are illuminated by monochromatic light, the avreage distance between...
  29. U

    Typical dimension of an apparatus for electron interference

    Greetings This is my first post in this section of PF. As the title says, I just want to know the typical dimensions of the two-slit experiment, intended for electron interference. That is, what are the slits made of, what is their spacing from the screen,source and from each other. Is...
  30. J

    Thin Film Interference- Transmission

    Homework Statement A thin layer of water (n=1.33) is surrounded by air what wavelength of light will not be transmitted through the water at the point where the water is 113 nm thick? The Attempt at a Solution - In phase - Path difference of 2T. - Constructive Interference I just...
  31. H

    Wave Interference in complex notaion

    Homework Statement Four waves of equal frequency ω are made to interfere. The amplitudes of the first two waves are equal (A), but those of the other two are equal to 2A. Their phase angles relative to that of the first wave are 0, ∏/3, ∏/4, and 2∏/3. Find the amplitude, frequency and phase...
  32. J

    Interference Patten in standing waves

    Please Help! Whenever i read standing waves, the interference patten can be seen as attached pictures. I want to know how this pictures can be taken? How lights can be interfered?
  33. A

    I have a very basic question about wave interference and more

    I have a very basic question about wave interference and more specifically electromagnetic wave interference. Suppose two beams of light each with amplitude A interfere with the same phase. the amplitude of the resulting beam is 2A. the two beams at the start have powers p= A^{2} each. The...
  34. S

    Doppler shift of an approaching source with interference problem

    Homework Statement P15. The police car with its 300 Hz siren is moving toward a warehouse at 30 m/s, intending to crash through the door. What frequency does the driver of the police car hear reflected from the warehouse? (5 marks) Homework Equations doppler shift for an approaching...
  35. S

    Interference of waves (check my hmwk questions please)

    For the first question, number 8 i have put up 2 attachment, one with the question the other one with the answer, I am not sure of the answers however, so if someone can check to see if theyre right or not, and if not show me how to attain the right answer. thanks For the next question, number...
  36. H

    Central Maxima & Interference: Investigating Intensity

    The central maxima is of highest intensity and then the successive maximas keep reducing in intensity. Has it got something to do with increasing number of waves which sort of interefere (the word has not been used in the sense of intereference pattern but as a normal english word) with the...
  37. F

    Constructive and Destructive Interference

    Homework Statement Two identical loudspeakers are located at points A & B, 2.00 m apart. The loudspeakers are driven by the same amplifier and produce sound waves with a frequency of 784 Hz. Take the speed of sound in the air to be 344m/s. A small microphone is moved out from point B along a...
  38. C

    Interference fit of a ring in a groove

    Imagine a thick cylinder with a retaining ring groove cut in the ID. I'm replacing the retaining ring with a split ring pressed into the groove. The split ring I'll have made along with the tool to install it. What I would like to determine is the amount of interference and the force...
  39. C

    Number of interference fringes visible in the central diffraction peak

    Homework Statement How many interference fringes are visible in the central diffraction peak if the ratio of slit separation to slit width is 3.125? Homework Equations d*sin(θ) = m*λ for interference maxima with slit separation d, maxima are at m = 0, 1, 2, 3 ... a*sin(θ) = m*λ for...
  40. W

    Thin film interference concept

    Hello, I am having some difficulties understanding this concept. It seems like wikipedia and my notes/teacher contradict each other According to my equation sheet, the equation for dark spots is 2nt = mλ and for bright spots is 2nt = (m + 0.5)λ. However, if a phase shift of 180 degrees occurs...
  41. E

    Interference in Thin Films, figuring out the phases

    Homework Statement I don't have a question on a specific problem, I am more caught up in the determination of the phases- I'll give a general problem to use as an example: In Fig. 35-41, light is incident perpendicularly on a thin layer of material 2 that lies between (thicker) materials 1...
  42. S

    Is there an interference pattern within a non-interference pattern?

    Consider two scenarios: Scenario 1: Single slit, single photons sent one by one. We would have a blob or column of dots. However inside this column is there an interference pattern hidden? Scenario 2: Double slit, single photons sent one by one, however we have instrumentation in...
  43. G

    Radio Frequency Interference (RFI)

    I am an electronics technician, and I work on various types of electronic equipment including radio communications devices which is the reason for asking this question. I was recently troubleshooting a radio communications malfunction, basically when squelch was broken, there was a “noise”...
  44. L

    How Does Path Difference Affect Interference Patterns in Light Waves?

    Homework Statement http://img5.imageshack.us/img5/4605/lchuynh177setphys52awee.png The figure shows the interference pattern that appears on a distant screen when coherent light is incident on a mask with two identical, very narrow slits. Points P and Q are maxima; Point R is a minimum...
  45. F

    Thin-Film Interference: Coating a Lens - Answers found, explanation needed

    Thin-Film Interference: Coating a Lens -- Answers found, explanation needed! Homework Statement Boxed answers are the correct ones. Homework Equations 2L=(m+1/2)(λ/n) for constructive interference (maximum reflection, bright film) 2L=(m)(λ/n) for destructive interference (minimum...
  46. G

    Double-slit diffraction with thin film interference

    Homework Statement A very thin sheet of plastic (n=1.70) covers one slit of a double-slit apparatus illuminated by 630 nm light. The center point on the screen, instead of being a maximum, is dark. What is the (minimum) thickness of the plastic? Homework Equations Constructive...
  47. 4

    Two particle interference (entanglement)

    Homework Statement A source emits pairs of particles "back to back", 50% into directions a1 and b1, 50 % into directions a2 and b2, where the choice between a1+b1 and a2+b2 is fundamentally undetermined. Insert Diagram A suppose that directions a1 and a2 are combined on a 50/50 beam...
  48. L

    Air wedge problem solving (single interference)

    Homework Statement 8 bright fringes are counted across 1.06 cm in the air wedge. Homework Equations Δx = L (λ/2t) The Attempt at a Solution i don't understand whether Δx is: 8Δx = 1.06cm or 7Δx = 1.06cm it said 8 bright fringes but Δx = the distance between...
  49. N

    Interference of electron waves in an atomic orbital

    I have a confusing question mainly due to my lack of understanding of Quantum Mechanics and spin! here it goes anyway... In an atomic orbital, like the 1s orbital, two electron waves with opposite spins occupy the same area of space. Now, does this mean that their waves should interfere with...
  50. N

    Constructive & destructive interference of light waves

    Homework Statement A glass-plate of 350 nm thickness is free standing in space. At the angle of 75 degrees, relative to the glass-plate plane, a white light point-source is placed. The diffraction (probably a typo, and should really be refraction) index of the glass is 1.33. On the same side...
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