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. 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...
  2. 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=...
  3. S

    What Determines the Point of Minimum Loudness in Speaker Interference?

    Homework Statement Hillary stands directly in front of speaker S1 and walks straight away (down on the page) from S1 as shown in the diagram. What is the first distance (measured from S1) at which she will hear minimum loudness? Speed of sound is 343 m/s and the frequency of the sound is...
  4. Dimani4

    Interference of different lights

    Hi ppl, I have a question to you. What happens if we approach two lasers with different wavelengths close together while they going in the same direction? ----------------> -.-.-.-.-.-.-.-.-.> did we get the interference between the different wave length of lasers result the different...
  5. B

    Wavelength and destructive interference

    Homework Statement In the figure the two speakers are producing identical sound waves. The solid lines represent constructive interference regions and the dashed lines represent destructive interference regions. The point labeled 1 is 662.15 m from the bottom speaker and 742.9 m from the...
  6. C

    Wick rotation and interference

    In light of the fact that Wick rotation can replace imaginary exponent wtih the real one, how does it reproduce interference? For example, in double slit experiment, how would we reproduce the fact that probability of reaching certain spots on the screen is zero? After all, the exponent of...
  7. N

    How to Solve Thin Film Interference with White Light?

    Homework Statement A 360 nm thick oil film floats on the surface of the water. The indices of refraction of the oil and the water are 1.50 and 1.33, respectively. The surface of the oil is illuminated from above at normal incidence with white light. The two wavelengths of light in the 400 nm...
  8. N

    Solving Thin Films Interference Problem with Oil and Water | 360nm Thickness

    Homework Statement A 360 nm thick oil film floats on the surface of the water. The indices of refraction of the oil and the water are 1.50 and 1.33, respectively. The surface of the oil is illuminated from above at normal incidence with white light. The two wavelengths of light in the 400 nm...
  9. 1

    Two-point source interference pattern

    Homework Statement A two-point source interference pattern is generated by sources operating in phase at 1.0 Hz. The sources are 2.0 m apart and the wavelength of the waves is 0.60 m. At what angles, measured from the centre line of the pattern, are the nodal lines produced located...
  10. S

    Interference using white light

    Homework Statement What will happen if we use white light at young's double slit experiment? Homework Equations interference The Attempt at a Solution Will we observe several colors on the screen because white light is composed from several light with different wavelengths? Thanks
  11. M

    Two-Slit Interference Question

    Homework Statement Suppose I have two different visible lights of different wavelengths passing through in a two-slit interference experiment. What appears on the screen is mostly a mixture of the two colours. However, one of the bright fringes, say m=2 is purely 1 of the colours (this light...
  12. T

    Interference and entanglement

    Hi All, I try to understand the outcome of following setup: The idea is that in the middle, a pair of polarization entangled photons are generated (so that the polarization of right-going and left-going are opposites of each other). The setup on left side is deviced so that if the...
  13. J

    Two Point Source Interference pattern

    Homework Statement Studying physics in High school, and for two years now we have covered two point source interference patterns with light, sound, and water wave in a ripple tank per say. The type of wave nor medium is necessary significant for me at the moment, but I am having trouble...
  14. H

    Exploring the Possibility of Inter-Dimensional Interference

    I believe the dual slit experiment proves that single photons and even buckyballs have to interfere with something right ? Even if it's only themselves ? So is it possible that they could be interfering with coppies of themselves from other dimensions ? Maybe 20 of them, as proposed by string...
  15. S

    Constructive or destructive interference- Car radio

    Homework Statement A car’s radio antenna is located at a distance of 56.983 m from a brick wall, which is assumed to act like a dense barrier. The car is attempting to listen to an FM radio station with a frequency of 89.5 MHz. These waves travel at the speed of light, 3.00 × 108 m/s. The...
  16. S

    Please explain human EM interference with my XMAS lights

    I am aware that the human body has electrical properties, But was baffled by what I witnessed Christmas Eve. I had a malfunctioning electric candle in the window. I picked it up to check the tightness of the bulb, and it immediately came on. I set it down and it went off. Three times this...
  17. P

    What is the Formula for Thin Film Interference?

    Homework Statement [PLAIN]http://img403.imageshack.us/img403/2696/33095583.jpg The attempt at a solution I simply took 425 nm and divided it by 4 by using the destructive reflection from thin film. I got 106 nm as my answer, which is c. Is this correct?
  18. J

    Construstive Interference of Waves. Why don't They cancel Out?

    Lets say there are two waves in the ocean exactly identical heading in opposite directions. It seems like logically they would cancel out since they are moving in opposite directions. Yet they don't cancel out and I can't figure out why. If two cars hit each other with same force in opposite...
  19. I

    Double Slit Interference Question

    Homework Statement Light of wavelength 680 nm falls on two slits and produces an interference pattern in which thefourth-order fringe is 38 mm from the central fringe on a screen 2.0 m away. What is the separationof the two slits? Homework Equations Sintheta=2m(\lambda2d)...
  20. fluidistic

    Optics, interference, very unusual problem

    Homework Statement See pictures for the data. Basically there's a transparent prism looking like an inclined plane and making an angle \alpha with the horizontal. Its base is 3 cm large and if we shine a vertical light of wavelength \lambda, we can observe an interference pattern as seen...
  21. A

    Interference pattern observed half-way into the formation

    We know that the interference pattern forms even when photons (or electrons etc.) are sent one at a time. The photons only land on the fringe parts of the screen and not the dark part - as if directed by some underlying information about where they are supposed to go. So far so good...
  22. S

    Destructive interference, two speakers

    Homework Statement Two speakers 14 m apart are emitting tones at a frequency of 1020 Hz. What is the closest distance (in m) from one speaker, along the line connecting the speakers, at which the sound intensity be will be zero? Homework Equations V= Lambda x f The Attempt at...
  23. P

    Artificial and Natural Radio wave interference

    Hi everyone, I'm a beginer in communication science. I have very fundamental question. We know that natural radio waves are emmited from sun to Earth (as a part of their electromagnetic spectrum); what will happpen if our communication devices uses radio waves of same frequency and wavelength...
  24. B

    Cell phone signal interference

    I'm not an engineer and so I appreciate everyone who contributes. 1)Is there any measurable cell phone interference from a car battery, alternator, or starter while the car engine is running if the cell phone is in the driver's seat? 2)What would this interference look like? Thank you.
  25. F

    Exploring Quantum Mechanics: Interference Experiments with Entangled Particles

    Hi, This is my first post here. I have done some reading on quantum mechanics and am curious to know more. I know about the double slit experiment and the interference pattern produced. I have also read of entangled pairs. My main question is: If you have a pair of entangled...
  26. J

    Far-field interference pattern in double slit experiment

    Homework Statement An interference experiment employs two narrow parallel slits of separation 0.25mm, and monochromatic light of wavelength \lambda = 500 nm. Estimate the minimum distance that the projection screen must be placed behind the slits in order to obtain a far-field interference...
  27. J

    What happens to the energy in case of destructive interference ?

    What happens to the energy in case of "destructive interference"? Hi everyone, I'll mention a few cases here. 1) In case of sound suppose we have two speakers. One gives off a certain sound and the other speaker gives off the exact inverted phase of the other speaker's sound, both with...
  28. S

    Thin film oil drop interference

    Homework Statement Hi all, i have a question on thin film interference. Lets say there is an oil drop on the surface of water. Light reflected from the oil drop is observed from above. Explain why interference fringes are not seen when the thickness of the oil drop increases...
  29. B

    Relay causes circuit interference?

    Hello, I'm working on a fire/burglary alarm panel and I need to add an external relay that closes a circuit whenever a fire alarm is detected (i.e. no voltage, just circuit closure). The alarm panel has one internal relay that activates for fire, and one that activates for burglary; each of...
  30. A

    Variable conditions of double slit interference

    Homework Statement Hi Can anyone help on this. The questions is as follows: In a double slits experiment using red light, a fringe pattern is observed on a screen at a fixed distance from the double slits. How would the finge pattern change if: a) The screen is moved closer to the...
  31. R

    What Color Will a 320nm Soap Film Appear in Reflected Light?

    Interference with thin film :( Homework Statement A soap film in air is 320nm. thick. If it is illuminated with white light at normal incidence, what colour will it appear to be in reflected light (assume that the index of the soap film is 1.33). Homework Equations The condition for...
  32. D

    Two slit interference question dont know how to begin

    Homework Statement Two slit interference question: A screen is 2.2m from two slits. The distance from point P to point R (the central maximum to the 2nd dark band) is 1.6mm. This is what the pattern looks like (l) means light band... (d) means dark band ......P...R (d) (l) (d) (l) (d)...
  33. C

    Interference Patterns in Optical Fibers: Causes and Solutions

    Hey all I am using optical fibers as a read-out medium form a PCB. I see interference in the data through this fiber. Can someone shed a light on the interference patterns on the optical fiber? Usually one should not see any electronic noise in fibers. How true is it and how to get around it...
  34. D

    Interference Pattern from a wedge

    Hi. What I have is a wedge with a flat surface at the top which I have 632nm light incident normal to the surface. What I want to be able to do is measure theta of the wedge. I am having trouble drawing the connection of the formula I have directly to the optical path length difference...
  35. C

    Interference at Odd vs Even Harmonics: Is the Square Wave Really Square?

    If I look at the Fourier transform of the square wave signal, the peaks are at the odd multiples. In the device that I am working on, I would expect the interference at the odd harmonics of the center frequency. But I see the interference at even harmonics. When is this possible? (Only if...
  36. Q

    How Thick Is the Oil Film for Red and No Light Interference?

    Problem A thin film of oil (n = 1.30) is located on a smooth, wet pavement. When viewed perpendicular to the pavement, the film reflects most strongly red light at 640 nm and reflects no light at 548 nm. How thick is the oil film? Equations and Attempt Refractive index: air - 1 oil -...
  37. I

    What Factors Affect the Distance of Strong Signals in Radar Transmission?

    Homework Statement Two radar transmission towers located 6.4 km apart emit identical signals of wavelength 420 meters. A ship located at a point 30 km equidistant from the towers experiences a strong signal from the towers. However, as it sails parallel to the line of the towers it...
  38. E

    Electron/photon interference pattern questioned

    The interference pattern created by the distribution of particles (electrons or photons) is related to the wave behavior. We interpret the probability distribution as the intensity distribution of 2 interfering waves. Say, a single electron travels toward the 2-slits, it diffracts like...
  39. S

    Interference of Waves Question

    Homework Statement Heres the question: Two towers of a radio station are 4.00 x 10^2 m apart along and east-west line. The towers act essentially as point sources, radiating in phase at a frequency of 1.00 x 10^6 Hz. Radio waves travel at 3.00 x 10^8 m/s. a) In which directions is the...
  40. M

    Wave interference in a car at speed

    I'm trying to figure out the interaction between the stereo of a car and the wind/road noise coming from outside. I was debating with someone about the interaction and argued that the stereo sounded diminished in volume level because of destructive interference. But I honestly don't know...
  41. W

    Checking for interference equation - two wave mixing

    Homework Statement Not too sure if my problem falls under this category. Hope I have done all formatting correctly Basically I am seeking some confirmation on my maths derivation and would like to enquire why there is discrepancies when we expressed the result in Fourier Spectrum...
  42. C

    Phase Difference for Interference of Traveling Waves on a Stretched String

    Homework Statement What phase difference between two otherwise identical traveling waves, moving in the same direction along a stretched string, will result in the combined wave having an amplitude 1.3 times that of the common amplitude of the two combining waves? Express your answer in (a)...
  43. S

    Double slit interference pattern

    Homework Statement Two slits are separated by 0.320 mm. A beam of 500-nm light strikes the slits, producing an interference pattern. Determine the number of maxima observed in the angular range -30 degrees < theta < 30 degrees. Homework Equations d*sin(theta) = m*(lambda) The...
  44. R

    How Do You Calculate Interference Fringes in a Double Slit Experiment?

    Homework Statement A laser beam ( λ = 694 nm) is incident on two slits 0.100 mm apart. Approximately how far apart (in m) will the bright interference fringes be on the screen 5.00 m from the double slits? Homework Equations y=L\left( \frac{m \lambda}{d} \right) The Attempt at a...
  45. H

    Constructive interference - energy non-conservation?

    Consider two identical optic fibers with deeply subwavelength tips. Let their tips be placed next to each other, at a distance much smaller than the wavelength. Let light of equal intensity come out of them in phase. Then, by the principle of linear superposition, at some distance much bigger...
  46. A

    Can Interference Patterns be Observed with Sound Waves?

    Homework Statement http://img337.imageshack.us/img337/285/64902163.png Homework Equations \Delta x = \frac{\lambda L}{d} where delta x is the fringe separation L is the distance from screen to signal source d is the slit separation The Attempt at a Solution Okay you see I'm using...
  47. P

    How Does the Central Maximum Shift When a Laser Beam's Angle Changes?

    Homework Statement A laser beam, with a wavelength of 532 nm, is directed exactly perpendicular to a screen having tow narrow slits spaced .15 mm apart. Interference fringes, including a central maximum, are observed on a screen 1.0 m away. The direction of the beam is then slowly rotated...
  48. C

    Witnessing Colorful Interference Patterns with a Benham Top

    When i spin a benham top why do i see colors , Is this because of the dashed black lines , that i am now pulsing white light , so now the white light is out of phase and the red , green , yellow photons are interfering so i see colors , Is this is what is going on .
  49. morrobay

    Double slit interference destroyed by observer or by photons

    When the electron double slit interference pattern is destroyed during measurement detection, to determine which slit the electron passed through, the explanation is that the observation is responsible. Given that detection is done with photons that can interact and alter the path of the...
  50. L

    Wave Interference at Radio Station Antennas

    Homework Statement The transmitting antenna for a radio station is 7.00km from your house. The frequency of the electromagnetic wave broadcast is 536kHz. The station builds a 2nd transmitting antenna that broadcasts an identical em wave in phase with the 1st one. The new antenna is 8.12km from...
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