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. E

    Interference from two radio antennae - simplistic and workings include

    Is this correct ? I have an issue for the minima formula when n=1 I get theta = 90 degrees. This doesn't make any sense. Is my method correct ?
  2. DrChinese

    Double-slit interference pattern measurement with entangled photons

    Although it is well known that a series of individual photons will build up an interference pattern in a double slit setup, there have been few (if any) experiments where such a pattern is built up by sending photons through one at a time. Here is a great experiment from one of the top quantum...
  3. N

    Thin Film Interference Problem: A hair is placed at the edge .

    Thin Film Interference Problem: A hair is placed at the edge... Homework Statement Thin Film Interference Problem: A hair is placed at the edge between two 10.0 cm glass plates of n= 1.52. Light of 400 nm wavelength shines on the glass and an interference pattern is formed. If the...
  4. M

    Quantum Eraser Interference Patterns

    I'm not clear as to how the overall interference pattern (or lack thereof) observed in the quantum eraser experiments (http://grad.physics.sunysb.edu/~amarch/ ) ends up being the same if the eraser is present or not present. My thinking follows. Say N entangled photons are sent through the...
  5. M

    Difference between interference and diffraction?

    Hi, I'm currently taking a Wave and modern physics class and we recently finished two chapt: interference and diffraction. I'm having a hard time grasping the difference. I understand that diffraction is the expansion of light when it goes through a small opening ( it "flares" out...
  6. L

    Interference and wave nature of light

    Two in-phase sources of waves are separated by a distance of 4.00 m. These sources produce identical waves that have a wavelength of 5.00 m. On the line between them, there are two places at which the same type of interference occurs. Where are the places located? I already know the...
  7. E

    Light Interference Wave Equation - Assumption

    Homework Statement Homework Equations In question. The Attempt at a Solution To be clear it's part (vi) that's unclear to me. In order to ignore the cosine term it has to reduce to 1. This can happen, only if k(x1+x2)/2 = ωt Is this a correct assumption ? Also, it is known that k = 2∏/λ...
  8. G

    Does Constructive Interference Double Sound Intensity at Source Point in Water?

    If two sound sources (A, B) are placed in a water tank and emit sound waves at the same frequency, phase and amplitude, if I measure the sound intensity at point A, will the detected signal will be ~double than the emitted signal of each sound source? I think that the answer is yes because of...
  9. E

    Wave interference and harmonic oscillation

    1. when wave is destructive interference ,where is the energy? for example, two plane wave have opposite phase ,they will destructive interference completely,but where is the energy? in antireflection film, the reflection wave is disappear!why? where is the energy? where is the wave? 2.in what...
  10. E

    Energy of twin source interference

    Homework Statement http://www.mediafire.com/view/?3efd7326e49kteb I've worked out all except part (iv). These are my workings : http://www.mediafire.com/view/?elswc5g5412zhzq I just can't see how to get rid of cos(pi*(x1+x2/λ -wt). Also, where does the I0 come from ?
  11. E

    Twin Source Interference - Radio Towers

    Homework Statement http://www.mediafire.com/view/?09c89b8986u5zls The above is a question from my problem sheet. I've got no idea how to attack this since its been very poorly explained in my lecture handouts. Can someone please help me ?
  12. Saitama

    Sound waves - Destructive Interference

    Homework Statement Two identical loudspeakers are located at points A & B, 2m apart. The loudspeakers are driven by the same amplifier (coherent and are in the same phase). A small detector is moved out from point B along a line perpendicular to the line connecting A & B. Taking speed of sound...
  13. H

    Double slit interference experiment

    If separate baffle around two different substances，What impact on the interference fringes？
  14. P

    Optics: Interference and Phase

    Homework Statement Two flat slides of glass are separated at one edge by a thin wire, as shown below. The top surface of the upper slide and the bottom surface of the lower slide have special coatings on them so that they reflect no light. The system is illuminated with light of wavelength...
  15. A

    Is There Room for Interpretation in Quantum Mechanics?

    Usually the only indication that a system (maybe particle) is in a superposition of different eigenstates of a particular observable is the finding of interference. I wonder if there is any interpretation that would consider the possibility of having a system (maybe particle) in a situation in...
  16. J

    Destructive Interference and coherent light in anti-phase

    I have a question about coherent light in anti-phase, I'm probably thinking about this wrong but I just can't understand what happens to the energy in the wave when two waves of the same wavelength, frequency and amplitude are in anti-phase as the resultant wave is 0.
  17. NATURE.M

    Thin Film Interference Problem

    Homework Statement Light strikes two plane sheets of glass with a thin air space between them as shown. If the light has a wavelength of 580 nm and the air space between the glass has a thickness of 870 nm, predict whether the reflected light as demonstrated by rays A and B will cancel or...
  18. R

    Standing Waves in Bohr's Circular Orbit: Interference Explained

    If electron waves weren't standing waves in Bohr's circular orbit, why and how would the waves interfere ?
  19. E

    Interference in Quantum Mechanics (Basic)

    I am doing some reading on Quantum Mechanics, and I do not understand this concept. Here is an excerpt from "The Universe and the Atom" by Don Lichtenberg. Sorry for the bad formatting. I don't understand why we can't answer which slit the particle when through. What else could it have gone...
  20. P

    Thinnest film that will give constructive interference for red light

    Homework Statement When a thin soap film is very thin, we see it as black. How thick (in nm) is the film in the region where we see the first red band? Take the wavelength of red light to be 752 nm and the index of refraction of the soap to be n = 1.33. Homework Equations [2nt/λ] - 1/2...
  21. I

    Air interference in a wi fi access point

    I will glad if you can help me to find information that explain what is it in easy way in two things that are related to communication 1. Air interference 2. wi fi access point
  22. B

    Two slits diffraction vs interference

    Hi, What is the difference in the setups of the Young's double slit experiment and the two slits diffraction? I found textbooks discuss each differently, yet I found no difference in the setup. Thanks to any help.
  23. I

    Do noise-cancelling headphones use spatial or temporal interference?

    Homework Statement Do noise-cancelling headphones use spatial or temporal interference? Homework Equations The Attempt at a Solution They use spatial interference, right? Temporal interference would cause beats which is not noise-cancelling.
  24. I

    What Are Frequency of Beats and Effective Frequency in Wave Interference?

    So my textbook says that the equation for the frequency of beats is |{ f }_{ 1 }-{ f }_{ 2 }| and the equation for effective frequncy is \frac { { f }_{ 1 }+{ f }_{ 2 } }{ 2 } , but what is frequncy of beats and effective frequency anyways? Edit: Opps. Should've posted it here...
  25. Q

    Young's fringes experiment, interference fringes

    Homework Statement (this is high school level) The pic below shows interference fringes observe in Young's fringes experiment: Explain why wider slits at the same spacing could produce fringes at the outer edges brighter than some of the fringes nearer the centre. Bear in mind there was a...
  26. S

    Double slit experiment - no interference in the vicinity of light

    Hi, I'm reading N. Zettili Quantum mechanics. In the "double slit experiment", when the beam of the electrons pass the the two slits, they present an interference pattern on the screen. But when we have a light source there to trace the electrons, we see what we have expected to see of the...
  27. S

    Why unequal fringe width in Michelson interference pattern?

    why unequal fringe width in Michelson interference pattern?
  28. D

    Wired USB devices shown to lose power due to RF interference

    I previously posted about an RF interference issue that was affecting a pair of Klipsch ProMedia 2.1 speakers here. I have since found that a neighbor living across the parking lot broadcasts transmissions of up to 2,000 Watts from his apartment, which has been the cause of this issue. I have...
  29. S

    Interference pattern calculations for unequal slits per QM theory

    I am trying to understand how QM theory (wave-functions) are applied to Interference pattern calculations for unequal slits for a single particle double slit experiment case 1: both slits are equidistant from the "center", however one slit is bigger and the ratio of the width between the slits...
  30. ?

    Sound interference experiments

    Hi everyone! I have to do an experiment in the lab related with interference in sound waves with same frecuency. I am just looking for ideas or suggestions. Thanks!.
  31. binbagsss

    How Does Changing Plate Distance Affect Interference Patterns in Interferometry?

    - why is it that fewer rings are observed when the plates are moved closer together (given wavelength , monochromatic source). What equation shows this relation? - Consider a non-monochromatic source, such as a Sodium Lamp, as the distance varies, both patterns change but at differnt rates -...
  32. binbagsss

    Interferometer and Interference.

    I have some questions regarding a fabry perot interferometer. (they aren’t problems as such however I have had a good look around the internet and am struggling to find what I’m looking for). 1) Why is it that a circular fringe pattern is observed. How does a single source interfere with...
  33. Q

    Calculating Wavelength from Interference Pattern: Narrow Slits and Laser Light

    Homework Statement Two narrow slits are cut into a sheet of paper and set in front of a laser beam, causing an interference pattern to appear on the wall. If the distance from one slit to the third bright fringe is 0.5000004 m and the distance from the other slit to the same bright fringe is...
  34. D

    How does temperature affect the position of interference fringes in thin slits?

    Homework Statement A very thin sheet of brass contains two thin parallel slits. When a laser beam shines on these slits at normal incidence and room temperature (20.0 ), the first interference dark fringes occur at 32.5 from the original direction of the laser beam when viewed from some...
  35. D

    Interference and slits question

    Homework Statement A radar tower sends out a signal of wavelength . It is meters tall, and it stands on the edge of the ocean. A weather balloon is released from a boat that is a distance out to sea. The balloon floats up to an altitude . In this problem, assume that the boat and balloon are...
  36. M

    Order of Dark Fringes: Understanding Interference Patterns

    See attachment please. After that, please point out, the order of the dark fringes. I mean I can't see where is m=0 dark fringe? Where to start? I want to know so I can know that radius enclosed by each fringe. Thanks.
  37. S

    Temporal complementarity- single and two-photon interference

    I am looking for: Any experiment/paper that shows - complementarity between single- and two-photon interference (coherence and entanglement) in the Temporal domain.
  38. E

    Wave Interference - the principle of superposition

    Homework Statement The problems are attached in the photo below (or at least I'm hoping they are, doing this from my Ipad makes this somewhat diffcult) Homework Equations Not really an equation, but the Principle of Superposition states that the amplitude of two interfering waves are added...
  39. L

    Sound interference and whistle

    Homework Statement A car honks a 2kHz tone and is 40m from a long high wall. A man is running parallel to the wall, 10m away from it, at 5 m/s, and is presently 30m away from where the whistle is closest to the wall. How many beats/second will be heard by the runner as he will hear the direct...
  40. A

    Question about the interference effect with two distinct sources.

    The optical two-source interference effect due to Hull (1949) has largely been overlooked by the history of quantum mechanics. Mandel and Fleegor brushed up the effect by reducing the signal strength of the sources and reducing exposure times for interference collection. In the end this effect...
  41. 0

    Grade 12 2-D Wave Interference

    Hello and thank you! I am having trouble understanding Mr. Thomas Young's equations for the double-slit apparatus with the bands etc. Specifically, for constructive interference: Length = PS1-PS2 = n(lamda) What I understand is that this n value is the phase shift in their wavelength...
  42. jaumzaum

    Where does interference occur in light waves?

    I'm really confused about the way the light can suffer interference. I'll try to explain the way I think all this occurs and the question I have if this explanation was correct. I would like you guys to correct me if anything I say is wrong and to try to explain me the final question. Light is...
  43. P

    Quick question on interference of light

    I've studied Young's slits and other diffraction type experiments and so understand how a light wave can interact and constructively or destructively interfere depending on path difference etc. My question is: why is this not more obviuos is everyday life? Say I'm looking at a cup placed on a...
  44. A

    Energy in destructive interference.

    Homework Statement What happens to the kinetic energy of the system when two pulses interfere destructively? Exact Question: Two pulses in a stretched string whose center are initially 8 cm apart are moving towards each other as shown in the figure(Attached). The speed of each pulse is 2...
  45. S

    Thickness of AntiReflection Coating for destructive interference

    Homework Statement Glass, despite being transparent, still reflects a little bit of light. When making lenses and such, you'd rather not waste any light with stray reflections. Fortunately, you can use destructive interference to suppress those reflections. The picture below shows a piece of...
  46. L

    Interference between two waves problem

    Homework Statement Assume that the waves from the sources are emitted in phase, and that at the point P, amplitude of the disturbance is zero. what is the wavelength of the traveling wave emitted by the sources? (there is more than one possible answer here,but provide the largest possible...
  47. C

    Interference Fit Problem involving changing deltas.

    Homework Statement Problem number 3 is the one I have the issue with. I attached it as a PDF file. Homework Equations Looking through my textbook, the equations that I think are relevant are: P=Eδ/2b[((c^2-b^2)(b^2-a^2)/(2b^2(c^2-a^2))] I am assuming the hub and the pipe are the...
  48. C

    Single electron single slit interference

    single electron diffraction through single slit Hi Guys Wondered if you could help me. Say a high energy electron (low wavelength?) is fired through an arrangement of atoms (single slit). How does a single electron hit a detector / screen according to a diffraction pattern? I understand...
  49. S

    Multiple Slit Interference - 3rd Slit Added Between 2 Slits

    Homework Statement Suppose a third slit of the same width were added halfway between the original two slits. (the original two slits were a distance d apart). When there were just 2 slits, the point C was the center (a principal max), point Z was the first maximum after C, point Y was the...
  50. C

    Thin Film Interference Question

    Homework Statement White light is sent downward onto a horizontal thin film that is sandwiched between two materials. The indexes of refraction are 1.80 for the top material, 1.68 for the thin film, and 1.50 for the bottom material. The film thickness is 5.24*10^-7 m. (a) Of the visible...
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