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. StevieTNZ

    Double-Slit Experiment & Wave Interference

    In regards to the double-slit experiment, where two waves cancel each other out (causing destructive interference), does that cancel out the particle too? I would assume all particles would form the light areas of the interference pattern. Just don't understand how the light/dark bands are...
  2. J

    Double Slit Interference Pattern

    I am trying to calculate how wide of a screen you would need in order to observe an interference pattern produced by Young's original real-life double slit experiment. He cut a single narrow slit (width ds) in a window shade, admitting a narrow sliver of sunlight into a dark room. He inserted...
  3. Z

    Cause of interference pattern in the Michelson Interferometer.

    The books say that interference happens basically between the light waves from the two mirrors. But it seems to me that the path difference between the pairs remains constant for all the waves (as long as both the mirrors are perpendicular to each other). So why do circular rings form? How does...
  4. V

    Thin-film interference Problem

    Homework Statement [PLAIN]http://img135.imageshack.us/img135/6027/physicsch3569.png Homework Equations 2L = (m + 0.5) (λ/n) for m = 0, 1, 2, ... (maxima - bright film in air) 2L = m(λ/n) for m = 0, 1, 2, ... (minima - dark film in air) The Attempt at a Solution Bright 2L = (10...
  5. 3

    What Does Each Symbol in the Interference Pattern Equation Represent?

    i have a class test tomorrow and I've been studying but i can't find this one equation in the textbook and was looking for some help. I am asked to 'determine the distance between a diffraction grating and a screen by using the interference pattern equation.' this is a practical exam and count...
  6. H

    Wave Interference and speakers

    Homework Statement You are standing 2.5m directly in front of one of two loudspeakers. they are 3m apart and both are playing a 686hz tone in phase. As you begin to walk directly away from the speaker, at what distances from the speaker do you hear a minimum sound intensity? Assume speed of...
  7. B

    Laser light interference on liquid metal. why?

    I wanted to make tiny movements of the Earth visible by reflecting laser light off liquid gallium metal. It did produce nice reflections on my wall, showing dramatic wobbles of very tiny movements of the liquid gallium. It did however produce light interference patterns which I cannot explain...
  8. P

    Wave Interference - Phase Difference

    Homework Statement I have another Wave Interference problem that I am having trouble with. http://img199.imageshack.us/img199/6104/questionsv.png Homework Equations [PLAIN]http://img151.imageshack.us/img151/3535/hintg.jpg The Attempt at a Solution f = 90.0 MHz λ =...
  9. C

    Question on thin film interference

    Homework Statement A piece of paper of thickness 15 * 10^-6 m is used to create an air wedge between 2 glass slides that are 7.25 cm long. If the wavelength of the light being used is 595 nm, how many interference fringes are counted across the entire pattern? Homework Equations delta...
  10. P

    Single and Double Slit Diffraction and Interference

    I have no idea where to start with these questions. I am pretty sure I have to use these equations 1. theta = tan^-1(x/D) 2. wsintheta = nlambda 3. dsintheta = nlambda Which order m of in the two-slit interference pattern will give the least uncertainty in the slit spacing, d? a) m = 1 b)...
  11. E

    Single slit interference and Diffraction Grating

    Lets say I have a double slit interference experiment set up. Now if I cover one slit what CHANGES would be observed ? I know I would see fewer bright fringes and that the intensity of the bright fringes would fall. Is there anything else ?In a different scenario I have a diffraction grating...
  12. S

    Destructive interference of sound

    Two loudspeakers are separated by 0.50 m on one wall of a room measuring 3.5 m by 7.0 m at a temperature of 22°C. Both speakers generate a constant amplitude sound of frequency 690 Hz, in phase with each other, radiating equally in all directions. What is the shortest distance x along the...
  13. P

    Wave Interference: Solving Homework

    Homework Statement [PLAIN]http://img18.imageshack.us/img18/6175/questionn.gif Homework Equations The Attempt at a Solution At M the waves are in phase and at P the waves have exactly (pi) phase difference. M and P are 2.00 m apart. So it would mean that the largest possible...
  14. T

    Interference Pattern: Find # Bright Fringes w/483nm Light

    Homework Statement Two slits are illuminated with 483 nm light. If the slits are separated by 0.84 mm and each have a width of 0.07 mm, about how many bright interference fringes will be seen in the region of the central diffraction maximum? Homework Equations 2nd = (m + 1/2)\lambda...
  15. A

    Is it necessary to talk about photons when discussing interference in light?

    If we use a white light in Young's Double slit Experiment, instead of monochromatic light,What will happen?What could be observed on the screen? http://C:\Documents and Settings\Aditya\My Documents\My Pictures/untitled
  16. D

    Sound Interference - Radio Broadcast

    Homework Statement Roger in ship offshore listening to baseball game on his radio. He notices there is destructive interference when seaplanes from nearby Coast Guard station fly directly overhead at elevations of 777 m, 970 m, and 1163 m. The broadcast station is 98 km away. Assume there is...
  17. I

    Please help me with..Destructive Interference

    Homework Statement Light of wavelength 460 nm falls on two slits spaced .3 mm apart. What is the required distance from the slits to a screen if the spacing between the first and second dark fringes is to be 4mm? Homework Equations Ydark= ((\lambdaL)/d)(m+1/2) Using ydark= .004 m d= .0003 m...
  18. J

    Motivation for 2-slit interference pattern

    Homework Statement Using the eigenstates of x_op, show that the probability of finding a system described by a wavefunction Psi(x) at a position between a and a+da is given by lY(a)l^2da. Comment on a connection to initial motivation for a wave function from 2-slit interference pattern...
  19. T

    What is the minimum thickness for destructive interference in thin film?

    1. Calculate the minimum thickness of the film for which the intensity of the reflected red ray is near zero. (This is AP Physics B 2010 (c)ii.) I found the wavelength in the film to be 4.81x10-7 m nf=1.382. 2L=mλ (destructive interference) The Attempt at a Solution My first attempt yielded a...
  20. B

    Destructive Interference: radio telescope, ocean, galaxy

    Homework Statement My solution isn't working out for this question. Radio waves of wavelength 125 m from a galaxy reach a radio telescope by two separate paths. One is a direct path to the receiver, which is situated on the edge of a tall cliff by the ocean, and the second is by...
  21. S

    How Does Gear Interference Affect Gearbox Design and Longevity?

    I'm designing a 2-stage gearbox for a project at school (15:1 ratio, must transmit 20 hp, for a full-time 10-year minimum life). I've come up with 2 basic gear combos for my layout: 1. 16,80,24,72 2. 16,80,16,48 I've done all the calculations for each layout such as making sure that the...
  22. A

    Thin Film interference: air wedge

    Homework Statement A pair of very flat glass plates, 7.41 cm long, touch at one end and are separated at the other end by a small piece of 44 gauge copper wire, 5.08×10−5 m in diameter. An air wedge is formed between the glass plates by this supporting wire. Light of wavelength 631 nm...
  23. J

    Thin Film Interference and phasing

    I am looking over thin film interference and am having some difficulty understanding when to know if a reflected ray will be 180 degrees out of phase or in phase. I know that a ray reflecting off a medium with a higher index of refraction will have a 180 degree phase change; and that a ray...
  24. D

    Young's interference experiment problem

    Homework Statement Figure 35-25 shows two sources S1 and S2 that emit radio waves of wavelength λ in all directions. The sources are exactly in phase and are separated by a distance equal to 1.5λ. The vertical broken line is the perpendicular bisector of the distance between the sources. (a) If...
  25. A

    How Many Interference Maxima Appear Within the Central Diffraction Peak?

    Homework Statement Light with a wavelength of 530 nm is incident on 2 slits that are spaced 1.0mm apart. If each slit has a width of .1mm, how many interference maxima lie within the central diffraction peak?Homework Equations sin( degree) = m(lambda)/d The Attempt at a Solution I have no...
  26. jegues

    Thin Film Interference Patterns

    Homework Statement See figure attached. Homework Equations The Attempt at a Solution Not too sure how to do this one. I tried thinking about what it was doing before the air was replaced with the liquid. With air, The first reflection would have no phase shift (glass...
  27. A

    Interference by electric field

    interference by electric field... first thing, is it possible? i was thinking , if we have a stationary charge and an oppositely charged plate with a small gap in it... and behind that plate, a screen is placed to obtain the patterns so obtained by the electric field passing through that...
  28. P

    How does diffraction cause interference

    Light normally doesn't interfere with itself because it is incoherent and unpolarized, right? So how is it that incoherent, unpolarized light passes through a circular aperture and interferes with itself? How does the aperture suddenly cause the light to be able to interfere with itself? In...
  29. S

    What does interference really mean?

    Homework Statement At a particular point on a screen illuminated by two slits, the path length from that point to the bottom slit is greater than to the top slit. Which of the following statements are true about the path-length difference between the two waves arriving at the screen? a...
  30. N

    What is the Difference Between Diffraction and Interference?

    Hello, could someone tell me what is the main difference between effects of diffraction and interference? For now, I think that diffraction is name for deviation of waves when they come to obstacle. And interference is phenomenon when two or more waves are in superposition in some point...
  31. D

    Would a Wave Plate Affect Interference in Young's Experiment?

    In Young's experiment, would we see interference if we put a wave plate to rotate the polarization in one of the path of the beam?
  32. R

    One dimension interference of waves

    Homework Statement Two speakers are placed on the x axis, they produce monotonic sound waves of the same frequency. There is a microphone also on the x axis, but far away from the speakers. It detects a sound minimum when the second speaker is 20 cm behind the first. Then it detects a maximum...
  33. JJBladester

    Diffraction Grating interference pattern

    Homework Statement This is the interference pattern on a viewing screen behind two slits. (image of 7 bright fringes with black fringes between every pair of bright fringes) How would the pattern change if the two slits were replaced by 20 slits having the same spacing d between...
  34. M

    How Do You Calculate Slit Separation in a Double Slit Experiment?

    Homework Statement Red plane waves from a ruby laser (694.3nm) in air pass through two parallel slits in an opaque screen. A fringe pattern forms on a distant wall and we see the fourth bright band 1o above the central axis. (Counting the central bright fringe as zero). Calculate the...
  35. F

    Interference of Waves: Two Point Sources in a Ripple Tank

    Homework Statement Two point sources in a ripple tank are generating waves with the same wavelength \lambda. They are placed a distance apart d = 5.5\lambda: --------------------------- | | | * | | ^ | |...
  36. C

    Help with Interference Homework

    Homework Statement I'm doing a lab and it says: Assume that on the double-slit plate, pattern A has exactly the slit separation printed on the plate. Shine the laser through pattern A onto a screen. Decide whether you will measure positions of maxima, minima, or both. Measure the...
  37. H

    Interference & Polarisation Questions

    1.in an intrfrnce expmnt. wit monochromatic light of wavlngth 6000 AU only 50 fringes are observable.estimate d coherence of d source. 2.show a circularly polarised lght is eqvlnt to 2 mutually perpendicular plane polarised lt wit a phase diff of pie/2. 3.fringes of equal inclination are...
  38. N

    What is the vacuum wavelength of the incident light in nm?

    Homework Statement When monochromatic light shines perpendicularly on a soap film (n = 1.33) with air on each side, the second smallest nonzero film thickness for which destructive interference of reflected light is observed is 296 nm. What is the vacuum wavelength of the light in nm...
  39. M

    Refraction, Diffraction, or Interference?

    Homework Statement Identify the following as an example of Refraction, Diffraction, or Interference 1) Rainbow pattern on a compact disk 2) The floating blotches in our eyes 3) Rainbow pattern on a beetle's back 4) The dark bands seen a a window screen Homework Equations...
  40. G

    Interference occurs, if two waves are said to be coherent

    hi, Our teacher told us, that interference occurs, if two waves are said to be coherent. but doesn't it have also something to do with the polarization of the two waves? so can one observe interference, if one has: circular or ellipctical polarized waves, when these two have a constant...
  41. S

    DECT 6.0 cordless phone and Wireless Internet - interference?

    Hello I just bought a new Panasonic DECT 6.0 cordless phone set (4 handsets) and recently subscribed to high speed DSL internet from my phone company. On my old corded/wired phones the phone connection audio qulaity was crystal clear. On the new DECT 6.0 cordless phones << Link removed...
  42. E

    Calculating Electron Interference Pattern Minima with Double-Slit Apparatus

    Homework Statement Electrons are accelerated through a 20 V potential difference, producing a mono energetic beam. This is directed at a double-slit apparatus of 0.010mm slit separation. A bank of electron detectors is 10m beyond the double slit. With slit 1 alone open, 100 electrons per...
  43. B

    Constructive Interference Eq'n

    Homework Statement Derive the equation 2t=(n+1/2)(lamba/index of refraction) to show it's the correct eq'n for constructive interference on reflection. Include a diagram. Homework Equations 2t=(n+1/2)(lambda/index of refraction) The Attempt at a Solution I'm not sure how you'd show...
  44. M

    Laser Interference and Diffraction, single and double slit experiment?

    Homework Statement I did the single slit light diffraction lab. The diode laser we used was 630-680 nm. It produced an image very much like the one on this page: http://hyperphysics.phy-astr.gsu.edu/hbase/phyopt/fraungeo.html#c1 How does having multiple wavelengths in the laser change...
  45. I

    Newton rings: spherical droplet with thin film interference

    Homework Statement So I have a similar situation with the traditional Newton rings. Instead of having however a convex lens, I have a (partial) spherical surface with height d with sitting on top of a thin film of thickness t, with d >>> t, and refractive index n and below the thin film is a...
  46. E

    Where does the first minimum appear in a double slit experiment with neutrons?

    Homework Statement In a double slit experiment, a beam of neutrons with speed 0.6m/s is diffracted by two apertures which are 0.05μm apart. a. What is the neutron wavelength? b. Where does the first minimum appear? Homework Equations \lambda = \frac{h}{p} dsin\theta =(m+\frac{1}{2})\lambda...
  47. C

    Wave interference on beachfront

    Homework Statement While walking along the shore at your beachfront home, you notice that there are two narrow gaps in the breakwater, the wall that protects the shore from the waves. These gaps are 9.0 m apart and the breakwater is 12.0 m from the shore and parallel to it. You go to the...
  48. D

    Circular Interference, Newton's Rings

    Homework Statement The figure below shows a lens with radius of curvature R lying on a flat glass plate and illuminated from above by light with wavelength λ. This photo, taken from above the lens, shows that circular interference fringes (called "Newton's rings") appear, associated with the...
  49. S

    Wire radius from interference fringes

    Homework Statement The diameters of fine fibers can be accurately measured using interference patterns. Two optically flat pieces of glass that each have a length L are arranged with the fiber between them, as shown below. The setup is illuminated by monochromatic light, and the resulting...
  50. C

    How Far Is the Farther Slit from the Nearer Slit in a Double Slit Experiment?

    Homework Statement Light of wavelength 500 nm illuminates a double slit, and the interference pattern is observed on the screen. At the position of the m = 2 bright fringe, how much farther is it to the farther slit than to the nearer slit? Homework Equations \delta=...
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