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. L

    Understanding Double Slit Interference: How Do We Count Fringes?

    Homework Statement When they say the first and third bright fringe, do they mean m=1 and m=0..do we count m=0? And likewise for when they say first and third dark fringe, is it m=1.5 and m=3.5? How would we know when to count m=0? Thanks Homework Equations The Attempt at a Solution
  2. F

    Calculating slit separation for sound two-slit interference?

    SOLVED Homework Statement A two-slit interference set-up with slit separation d =0.30 mm produces interference fringes at a particular set of angles THETAm (where m = 0, 1, 2,) for red light of frequency f = 4.9×10^14 hz. If one wishes to construct an analogous two-slit interference set-up...
  3. L

    Interference and Diffraction Combined

    Homework Statement Can anyone explain to me how exactly this works because i thought that interference is supposed to oscillate up and down at the same height but in the "interference and diffraction combined" pattern, it's no longer the case...And also, I'm not sure but in the "interference...
  4. A

    How Do You Distinguish Between Interference and Diffraction in Wave Experiments?

    interference vs diffraction ?? given a question with two or more slits , how to determine if it is interference or diffraction?
  5. O

    Transverse Wave Interference

    Homework Statement Having two identical waves, knowing how much they're out of phase with each other, how can I know the amplitude of the resulting wave (as a factor of the original amplitude)? Homework Equations The Attempt at a Solution
  6. R

    Double Slit Interference and linear distance

    Homework Statement In a double-slit interference experiment, the wavelength is 579 nm, the slit separation is 0.12 mm, and the screen is 30.0 cm away from the slits. What is the linear distance between adjacent maxima on the screen? [Hint: Assume the small angle approximation is justified and...
  7. R

    Destructive Interference and Min. Distance

    Homework Statement A steep cliff west of Lydia's home reflects a 1205 kHz radio signal from a station that is 63 km due east of her home. If there is destructive interference, what is the minimum distance of the cliff from her home? Assume there is a 180° phase shift when the wave reflects...
  8. S

    Produce an EM wave through interference

    I am trying to understand why it is not possible to produce an EM wave through interference that is completely different from the source waves. For example why can't 2 or more EM waves outside the visible spectrum add up to produce light? I haven't had any physics since high school and I don't...
  9. I

    Thin film light interference question

    Homework Statement A uniform film of oil (n=1.31) is floating on water. When sunlight in air is incident normally on the film, an observer finds that the reflected light has a maximum at wavelength (lambda) = 450nm and a minimum at wavelength (lambda) = 600nm. What is the thickness of the...
  10. L

    How Does m=2 Affect the Path Difference in Double-Slit Interference?

    Homework Statement I was just wondering in double-slit interference, when it's a bright fringe, let's say m=2, does that mean that one wave coming from one of the slits is traveling 2 wavelengths longer than than the other wavelength coming from the other slit? How does that work? Thanks...
  11. K

    How Does Destructive Interference Occur With Different Sound Wavelengths?

    Homework Statement Two speakers, one directly behind the other and along the x-axis, emit sound waves along the x-axis. The speaker in the back emits sound with a wavelength of .02 m and the speaker in the front emits waves with a wavelength of .05m. If the two speakers are separated by 3 m...
  12. J

    Interference of Waves Lab: Teach Grade 12 Physics

    Hi, I am a grade 12 physics student and as our final evaluation I must teach a section of our textbook to the class. The section I received was "Interference of Waves" and I must also create some kind of lab or demonstration for the class. My idea so far is to set up two speakers playing the...
  13. F

    Optical Path Length Difference & Constructive Interference: Normal Incidence

    Homework Statement Light falls at normal incidence onto a transparent film on a substrate as shown i. what is the optical path length difference in the case of normal incidence? ii. if nf>no and nf>ns, what is the condition for constructive interference in the case of normal incidence...
  14. I

    Does destructive interference contradict the law of conservation of energy?

    When two waves that are 180 degrees out of phase interfere, the energy from both cancels out. Why is it that, for example, a sound wave, which is a form of energy, can disappear when combined with another when the Law of Conservation of Energy states that energy cannot be destroyed? I posed...
  15. S

    Wave Interference and wavelength

    Homework Statement In Fig. 17-35, sound with a 15.6 cm wavelength travels rightward from a source and through a tube that consists of a straight portion and a half-circle. Part of the sound wave travels through the half-circle and then rejoins the rest of the wave, which goes directly...
  16. T

    Constructive and Destructive interference

    Hello guys I have a question about constructive/ destructive interference. I know that in single slit and double slit patterns that the dark fringes=destructive interference (minima) bright fringes = constructive interference (maxima) I do know that the formula's are as follows...
  17. S

    Calculating the Distance Between Interference Maxima: Yellow Light

    Homework Statement a)Yellow light Lambda= 589nm falls on a double slit. The distance between two slits is d=0.5 mm the width of each slit is a=100 micrometer. A screen showing the interference pattern is located 4 m behind the slits. Homework Equations What is the distance between...
  18. B

    Interference Pattern w/ D ~ d: Qualitative Analysis

    A simplifying assumption in determining the interference pattern from a double-slit experiment is to assume that the screen distance, D, is much larger than the slit separation, d. This allows us to make the approximation that the two optical rays are parallel as they travel to the common...
  19. maverick280857

    Simulating Intersymbol Interference on channels

    Hi I'd appreciate help with the following problem: Suppose I have a Bayesian metric for navigating a trellis to detect the maximum likelihood sequence on a channel corrupted by ISI. The usual Viterbi algorithm works on the usual ML (nonstochastic channel) metric. Now, given the expression for...
  20. M

    Interference - Finding distance between slits

    Homework Statement A laser is shone through a set of slits and onto a screen. I have a Δy vs. L graph plotted, where Δy is the spacing between successive nodes, and L is the distance from the slits to the screen. I'm supposed to find the spacing between the center of the slits. The value of λ...
  21. T

    Double Slit Interference (nonzero slit width)

    Homework Statement A mask with 2 slits is illuminated by a light of 589nm wavelength. Slits each have a 0.1mm width separated (centre to centre) by 3.0mm. Calculate the distance between adjacent bright fringes on the screen if a screen is placed 5.0m away from the slits. Homework...
  22. M

    Calculating Minimum Width for 5 Interference Maxima

    Homework Statement Ramon has a coherent light source with wavelength 554 nm. He wishes to send light through a double slit with slit separation of 1.5 mm to a screen 90 cm away. What is the minimum width of the screen if Ramon wants to display five interference maxima? Homework...
  23. T

    Constructive wave interference problem

    Homework Statement A sheet of glass is coated with a 505nm thick layer of oil (n = 1.42). For what visible wavelengths of light do the reflected waves interfere constructively/destructively? Homework Equations For constructive interference lamba=2nd/m For destructive...
  24. R

    What is the approach for finding fringes on a screen with three slits?

    Homework Statement There are three slits in a screen, with one aligned with the source at z=0, one a distance a above 0, and one a distance b below 0. Another screen is at a distance d >> a,b from the first. What is the periodicity of fringes on the screen? Homework Equations \Delta \phi =...
  25. I

    MWI, decoherence, and interference

    I've been thinking about the many-worlds interpretation and how one might test it experimentally. I'm wondering if it might be possible to observe interference between macroscopic systems in different "worlds". We start with an isolated quantum system in superposition, and we let it interact...
  26. Y

    Interference fringes between rectangular pieces of glass

    hello again folks, this is the last problem that I haven't gotten in this week's homework. see attached image. Homework Statement Two rectangular pieces of glass (see attached image, I painstakingly made it with a very fussy/crash-ey program) are laid on top of one another on a plane surface...
  27. C

    Interference : GPS Transmission

    The GPS (Global Positioning System) satellites are approximately 5.18 m across and transmit two low-power signals, one of which is at 1575.42 MHz (in the UHF band). In a series of laboratory tests on the satellite, you put two 1575.42 MHz UHF transmitters at opposite ends of the satellite. These...
  28. T

    Solved: Wave Interference Frequency & Phase Constant

    Homework Statement 2 sources emitting radio waves of the same frequency are placed at x=0 meters and x = 1.2 meters. There are nodes at x= 0.344m, x= 0.719m, and x=1.094m. What is the frequency of the 2 sources and the difference in their phase constant Homework Equations The...
  29. X

    Calculating Maxima in 1-D Wave Interference with a Half-Silvered Mirror

    Homework Statement Monochromatic light of wavelength \lambda = 400 nm enters at A. It impinges on a ‘half-silvered mirror’ B, which directs some of the light to mirror C, while passing the rest to mirror D. Some of the reflected light from mirror C passes back through the half-silvered mirror...
  30. M

    Problem and thoughts about simple light interference

    1. With the later on given info, is it possible to through geometry calculate the wave length of a HeNe Laser? 2. Homework Equations and facts A Helium Neon laser emitts light through a double slit and towards a screen where a central image and the first dimmer bands can be seen. The...
  31. A

    How Far Can Sound Wave Interference Be Detected in an Auditorium?

    Homework Statement Two speakers are mounted on a wall in an auditorium. One is at floor level and the other is 3 m directly above the first. The speakers emit sound waves in phase at a frequency of 686 Hz. A line is drawn on the floor, perpendicular to the wall beginning at the lower speaker...
  32. N

    What is the thinnest film for strong reflection of visible light?

    Homework Statement A very thin oil film(n=1.25) floats on water(n=1.33). What is the thinnest film that produces a strong reflection for visible light with a wavelength of 700nm? Homework Equations \lambda=(2nd)/(m-0.5) d=(m-0.5)*(\lambda/2n) thinnest film has m=1 The Attempt at a...
  33. K

    Radio waves: constructive and destructive interference 1-dimension

    Homework Statement Two coherent sources of radio waves, A and B, are 5.00 m apart. Each source emits waves with wavelength 6.00 m. Consider points only along the line connecting the two sources. (a) At what distance from source A is there constructive interference between points A and B...
  34. R

    Multiple-Slit Interference (Again)

    Homework Statement Consider the original double slit pattern from problem 1. Suppose that a third slit with the same width were added halfway between the original two slits. So that d goes from being 1 to being 0.5 for both. Would point Z be a principal maximum, minimum, or neither...
  35. R

    Calculating Minimum Angle in Multiple-Slit Interference

    Homework Statement "If the distance between the centers of adjacent slits in the five-slit mask is 125[lambda], determine the angle (measured relative to the normal to the screen) to the minimum closest to the center of the screen." Homework Equations So, I have a question about the...
  36. X

    Optics and thin film interference question.

    Homework Statement The thin film is of two glass with air in the middle. refractive index of... air: n=1.0003 glass: n=1.5 lamba=632.8nm Q1.) Calculate optimum thickness of the film (for 1st order interference) Q2.) Why does the distance between interference fringe beome longer...
  37. B

    Calculating visibility of interference fringe

    Homework Statement A photomultiplier (PMT) is arranged to detect the photons from a double-slit experiment. It is placed at a point P in the detection plane and makes an angle \theta with the horizontal of one of the slits. Assume that the two slits have different widths and that the widths...
  38. S

    Destructive Interference of Light in 165nm Bubble Film

    Homework Statement Light waves of which wavelength will destructively interfere due to the thickness of the bubble film? The bubble film thickness is 165 nm, with an index of refraction of n = 1.3. a= 430 nm b= 650 nm c= 860 nm d= 285 nm (different wavelengths) Homework Equations...
  39. P

    Diffraction and Interference

    Homework Statement An aircraft causes a horizontal layer of charged particles to be formed in the atmosphere. Radio waves are relected without phase from this layer. Radio waves of frequency 8.00 x 10^2 kHz are received at a location 12 km from the transmitter. What is the minimum height of...
  40. P

    Two Radio Transmitters, Interference, and Waves

    Homework Statement FM station KCOM ("All commercials, all the time") transmit simultaneously, at a frequency of 97.1 MHz, from two broadcast towers placed precisely 32.44 m apart along a north-south line. (a) What is the wavelength of KCOM's transmissions? Homework Equations...
  41. C

    Double slit and thin film interference

    While completing my problem set for this chapter, I came across 5 problems I could not solve. I thought it might be rather annoying if I posted six posts, so I'm putting all my work and such here. I don't expect one person to try to help me with all of them, just one or two at a time will do...
  42. A

    Destructive interference of direct and reflected rays

    QUESTION: Astronomers observed the interference between a radio wave arriving at their antenna directly from the Sun, and on a path involving reflection from the surface of the sea. (http://i62.photobucket.com/albums/h101/kaikibana/problem1.jpg) Assume that the radio waves have a frequency...
  43. M

    What is the wavelength of the sound waves emitted by two speakers?

    Homework Statement Two loud speakers emit sound waves of the same wavelength.When a microphone is moved between them quiet places are observed 20cm apart.What is the wavelength of the sound waves? Homework Equations The Attempt at a Solution
  44. P

    Interference and diffraction of light

    Homework Statement green light of wavelength 5000 A is incident normally on a grating, and the 2nd order image is diffracted 32 degrees from the normal. how many lines/cm are marked on the grating A=10^-10 n= 2 degree= 32 d=? wavelength- 5000 A the answer to...
  45. GRB 080319B

    Laser Beam Destructive Interference

    If two lasers are pointed emitting end to emitting end in a vacuum (for lowest divergence), and emit 2 beams of light 180 out of phase, could both beams destructively interfere completely (no light coming from either emitting end after the beams converge)? If the experiment was done under...
  46. S

    Film interference with light and refration

    ok so i know why this happens but I am just not sure how to see how thick the film would be, I am not sure if your supposed to use the equation dsin(-)=wavelength someone help please thanks! You are outside in the Sun blowing bubbles. As you raise the round wand to blow bubbles, you notice an...
  47. G

    A way aroung determining which-paths in interference patterns?

    In Brian Greene's book 'The Fabric of the Cosmos' he introduces an experiment called the "delayed-choice quantum eraser". This was really a magnificent experiment at first sight but pretty unclear when I was done reading the results. The experiment basically goes like this: In each path that...
  48. S

    Optimizing Thin Film Interference for Maximum Reflection

    Homework Statement A transparent oil with an index of refraction of 1.25 spills on the surface of the water (n=1.33), producing a maximum of reflection with incident orange light (\lambda = 602nm in air.) Determine the lowest possible thickness (in nm) of the oil slick.Homework Equations...
  49. N

    Thin Film Interference Help?

    I don't have a particular homework inquiry to ask, just some questions I have about thin-film interference and its related equations. I was told by my instructor to learn these concepts on my own and I am just having a few problems I want to clarify. 1) Equations related to thin-film...
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