What is Destructive interference: Definition and 126 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

    I Delayed Choice Quantum Eraser with altered beam splitter

    Hi People, In Kim's real setup for interference patterns we use a beam splitter as 50:50 (reflectance,transmittance rate), lets assume we use 20:80 (%20 reflectance, %80 transmittance) for beam splitter what could we observe in this situtation on detectors (except D3,D4)? Dont forget we use...
  2. Addez123

    B What is causing destructive interference in double slit experiment?

    When you do the double slit experiment with photons or electrons you get a wave pattern. At certain points no electrons are detected. This is said to be caused by destructive interference. Destructive interference of what? If we shoot single electrons, one at a time, from where is this...
  3. S

    I Laser and hair - scattering or destructive interference?

    There is a video, where the author shows the interference of laser beam on a strand of human’s hair: I bought a laser pointer and reproduced this experiment. Indeed, when a single hair is placed on the way of the laser beam, I see the “scattering” picture (a series of points with intervals of...
  4. D

    B Does Destructive Interference Affect Starlight in a Double Slit Experiment?

    In this MIT course video, he shows on an optical table that in certain cases, when destructive interference occurs the light is going back to the laser (fast forward to 5:22 in the video below) My question is when I do a double slit experiment with starlight by putting 2 slits in front of my...
  5. M

    B Destructive Interference in the sound of multiple firecrackers set off at once?

    There is a massive and continuous fireball as fire crackers are exploding, generating thousands of shockwaves. Perhaps they are bouncing off each other and cancelling each other out like noise cancelling headphones,
  6. M

    I Energy of Electromagnetic Waves in Destructive Interference

    Hello ! As we know by definition that: "Constructive interference occurs when the phase difference between the waves is an even multiple of π (180°), whereas destructive interference occurs when the difference is an odd multiple of π." But my question is in the case of destructive...
  7. Q

    B What is Destructive Interference?

    In an electromagnetic interference pattern with two sources of identically sized waves, the dark areas are where the waves destructively interfere. Being identical in size, the waves should completely cancel one another out, leaving an area empty of any trace of electromagnetism. Yet the area of...
  8. J

    Solving Destructive Interference: Angle vs Wavelength

    The destructive interference equation for small angles is angle=wavelength/(2a), where a is the width. I assume it means destructive interference since its talking about areas where no light is present. Using the equation after changing degrees into radians I get the answer of 2491 nm when the...
  9. J

    Destructive interference through a narrow slit

    So I thought angle=wavelength/width of slit But when I solve for the width I got the wrong answer of 4567 nm, when the answer is suppose to be 130881 nm. I figured out that I needed to multiply my incorrect answer by 28.7, but where does this constant come from? Its not part of the equation...
  10. J

    Finding closest distance that will generate destructive interference

    So I can calculate wavelenghth using v/f to get 6.24. Now I made d1=sqrt(4.6^2+d^2) and d2=d so my equation now looks like sqrt(4.6^2+d^2)-d =6.24(n-1/2). To find n I made d=0 4.6=6.24(n-1/2) n=1.24 Now my problem is that I don't know which n to use or if I've even done the...
  11. ItsKurious

    Interference of light by splitting the wavefront and recombining

    In the above diagram, I have illustrated what is written in the summery. So, if the thickness and refractive index of the material are chosen such that the part of the wave that travels through the slab acquires a path difference of λ/2 and at the right end if I keen another convex lens so as to...
  12. S

    Constructive, destructive interference help please

    hi, i understand how to get to this equation, and this is the equation that gives the answer. However, the question asks for dark fringes which is destructive interference? would you not use m/2? so instead of the denominator (2*t) would it not be (4*t)? thanks in advance!
  13. H

    Destructive interference near two speakers

    where x is the distance from one speaker 343=(66)(5.197) wave length =5.197m x-(50-x)=(5.197)(m+0.5) I choose m=-10 2x-50=(5.197)(-9.5) x=0.314m? Prof says correct answer is 1.6m tho
  14. S

    Optics: Destructive Interference

    I thought if the question asks for the first minimum or the first dark fringe you use (m+1/2) but i am not getting the right answer. I was hoping if someone could tell me in what situations the (m+1/2) would apply? Thanks in advance.
  15. Kharrid

    Two Speaker Destructive Interference

    I already have the solution in front of me, I am wondering why there is a difference in the formula for path difference. I've attached the problem as well to show the Figure. What I am struggling to grasp is why the path difference for the angles closer to A is dsin(Θ) = (m+1/4)λ while the path...
  16. PainterGuy

    Constructive and destructive interference

    Hi, It said that constructive interference has taken place between two waves if the combined amplitude for two waves at a certain time is more than their individual amplitudes. Likewise, in case of destructive interference, the combined amplitude is less than the individual amplitudes of either...
  17. J

    Destructive interference in Unpolarised light

    Destructive interference is excellently demonstrated in Young's double slit experiment, where dark regions are formed due the waves being out of phase. However, what really confuses me is that unpolarised light has intensity. Assuming we had perfectly unpolarised light, as in where the...
  18. A

    "Total" destructive interference of plane waves

    Hello. Let's suppose that we have a Michelson interferometer to study interference patterns of light. This time we use plane waves. If we set the whole thing up so that the two separated beams have a phase difference of π when they superpose, destructive interference ensues. Since we're...
  19. T

    Destructive interference for distance-specific illumination?

    From a practical standpoint, can we combine two (or more) lasers tuned to almost-but-not-quite identical frequencies to create distance-specific illumination? For instance, say we have a 1 micron laser and a 0.9999 micron laser which we combine through some beam-combiner optics. In theory I...
  20. S

    Can you please check this (destructive interference).

    If it is wrong can you please pinpoint where i am going wrong. Thank you. 1. Homework Statement https://imgur.com/a/0STmmWt (uploaded picture because it has a diagram) Homework Equations To sense destructive interference , the person must be one half wavelength (0.5λ) closer or farther from...
  21. prodo123

    Frequency at which no destructive interference occurs

    Homework Statement Two speakers A and B, 2.00 m apart, produce a sine wave at the same frequency and phase. A microphone is placed on the line BC perpendicular to AB, at a distance x from B. The speed of sound is v=344 m/s. For a frequency ƒ low enough, there will be no destructive...
  22. A

    Newton's Rings and Thin Film Interference

    Homework Statement A total of 31 bright and 31 dark Newton's rings (not counting the dark spot at the center) are observed when 550-nm light falls normally on a planoconvex lens resting on a flat glass surface. How much thicker is the center than the edges? Homework Equations 2t = mλ 2t =...
  23. S

    Finding the Minimum Thickness for Destructive Interference in Thin Films

    Homework Statement A uniform film of TiO2, 1036 nm thick and having index of refraction 2.62, is spread uniformly over the surface of crown glass of refractive index 1.52. Light of wavelength 515 nm falls at normal incidence onto the film from air. You want to increase the thickness of this...
  24. A

    Diffraction Grating and White Light Problem

    Homework Statement White light containing wavelengths from 400 nm to 750 nm falls on a grating with 6000 lines/cm. How wide is the first-order spectrum on a screen 2.0 meters away Homework Equations dsinθ=mλ for constructive interference dsinθ=(m+1/2)λ for destructive interference Δx = λL/d...
  25. T

    Wave constructive destructive interference

    Homework Statement The figure shows two sets of water waves, created by two sources labeled "A" and "B." The solid half-circles represent wave crests from A, and the dashed half-circles represent wave crests from B. Suppose that individual wave crests from either source A or source B alone are...
  26. J

    Coating Eyeglass Lenses(destructive interference)

    Homework Statement Eyeglass lenses can be coated on the inner surfaces to reduce the reflection of stray light to the eye. If the lenses are medium flint glass of refractive index 1.62 and the coating is fluorite of refractive index 1.432, (a) what minimum thickness of film is needed on the...
  27. Daniel Petka

    Can destructive interference cause energy loss and how can it be regained?

    This is a really silly question and its bugging me. Do I lose energy through destructive interference? If not... then how can I get back what I invested before? Thanks, hope I understand the waves soon :)
  28. Vanessa Avila

    Light (Constructive/Destructive Interference)

    Homework Statement This is not a homework question but I would like if someone could explain to me when to consider what equation constructive/destructive? I learned these two equations very vaguely in class: dsinθ = mλ or d(ym)/L=mλ dsinθ = (m+1/2)λ or d(ym)/L = (m+1/2)λ The power point...
  29. T

    Nonreflective Coating and Emission Relation?

    Hi all, I've been able to find the answers to most of my questions in these forums, but this time I was not able to. So here goes my first post: I've been learning about thin film interference, and it all makes sense to me except for the correlation between destructive interference caused by...
  30. W

    Question on destructive and constructive interference

    Homework Statement Two speakers A and B are 3.50m apart and each one is emitting a frequency of 444Hz. However because of signal delays, speaker A is 1/4 of a period ahead of B. Find all points relative to the centerline between A and B where there is constructive interference. Include angles...
  31. Biker

    Constructive and destructive interference

    Homework Statement Suppose you have two pulses, One is a trough, It's amplitude is 3 cm and the other is a crest and its amplitude is 9 cm. Assuming they have the same wave length when they overlap the energy of the created wave is: 1- 1/16 E 2- 1/4 E 3- E 4- 4E Homework Equations ##E## is...
  32. Chris Frisella

    Does Destructive Interference Cancel Energy?

    Does it cancel it, or just create an equilibrium of forces upon a point(s)? Example: If you had a string and you sent a wave down one end, and the opposite wave from the other, once they meet there will be an instant when the string is flat as if there had never been waves introduced. But, if...
  33. Quantum of Solace

    B Destructive interference and conservation of momentum

    If two photons traveling in the same direction but out of phase cancel each other out, what happens to the energy and momentum?
  34. Apoorv_7

    Can Audio Cancellation Occur in Space?

    Homework Statement I created a 180 degree phase shifted version of a song using matlab. They cancel each other out when i play them together using any mixer software,but do not do so when i play the actual and the shifted versions from different sources. Homework Equations Is this possible.Can...
  35. I

    Destructive Interference in Water but not Air

    Homework Statement Consider a given monochromatic component of sunlight. The electric field drives a given air molecule. Each oscillating charge of the air molecule radiates waves in all directions, some of which travel to the eye of a given observer. But, for a given molecule (call it No.1)...
  36. C

    Optics - destructive interference

    Homework Statement White light (most intense at 550nm wevelength) shines on a layer of water (n=1.33) setting on a sheet of plastic film (n=1.25). What minimum thickness of water will produce destructive interference on the surface?[/B]Homework Equations a) phase reversal of light reflecting...
  37. SDewan

    Destructive Interference of two waves

    On a single long string, two sinusoidal pulses are started from either end. They have a destructive interference. Both the pulses have kinetic as well as potential energy. Now the point at which they meet, there being a destructive interference, no crest or trough is formed. But right after...
  38. G

    Destructive interference at a surface

    Take two lasers of the same intensity and wavelength and aim them at 30 degrees at the same spot on a mirror, so that at the surface the waves cancel perfectly. What happens? How can the wave be reflected if there is no field present?
  39. N

    Phase plus Antiphase radio waves

    If you produced a focused beam from, say, a cassegrain transmitter which consisted of two waves merged but one inverted what would be the result. I presume there would be destructive interference. My question is, where does the energy go?
  40. G

    Destructive Interference of 2 Lasers?

    If I have 2 identical laser pointers, is it possible for me to point them both at the same spot on a wall and see no light at all due to complete destructive interference?
  41. 24forChromium

    Destructive interference and energy

    Where do the energy go in a pair of photons that are annihilating each other exactly? What happens when they collide with something that absorbs photons like an electron? (I think electron can absorb the e. in a photon to jump into a higher level) Would this light wave become undetectable like...
  42. S

    What is the trough in destructive interference of EM?

    My textbook says that the trough of the electromagnetic wave cancels out when it meets a crest. Okay, that makes sense, but if the crest is the actual photon/wave of energy, what is this trough that can cancel out the energy? It seems to mean that there are "negative energy photons" in between...
  43. thalassa

    Is there constructive or destructive interference?

    Homework Statement Two sound sources are coherent and in phase. Is there constructive or destructive interference at the midpoint between the speakers? Homework Equations Generally, there is constructive interference whenever the path-length difference is an integer times the wavelength...
  44. Z

    Destructive interference Sound question

    Homework Statement A student enters Best Buy prepared to buy a pair of speakers. Before he does so, he conducts an experiment with them. He places the speakers 4.0 m apart and connects a signal generator to both speakers that produces a single and consistent tone. (constant wavelength and...
  45. Jilang

    Is polarised light a result of destructive interference?

    This question is prompted by a recent discussion I have been following regarding the insertion of a 45 degree angle polariser between two polarisers at 90 degrees to each other. The insertion of the filter seems to restore missing components which would suggest that those components were present...
  46. gracy

    Constructive interference and destructive interference

    Is he right there? Is there a principle that says "For every constructive interference, there is an equal (but opposite) destructive interference?" Is it impossible for constructive interference to occur without any destructive interference?I don't think so.Because when there is a constructive...
  47. Maged Saeed

    Points of destructive interference of sound waves?

    Homework Statement Two speakers (S1,S2), emitting sound waves of frequency 340Hz and separated by a distance of 3 m, are driven by the same oscillator. A listener starts walking from point A to S2 Along the line that joins A and S2> How many points of destructive interference will be observe...
  48. S

    Destructive interference and constructive interference

    Two loudspeakers are placed facing each 4.0 m apart. The speakers emit sound in phase with a frequency of 266 Hz. An observer at the center (2.0 m from each speaker along the line joining them) experiences constructive interference. The speed of sound is 343 m/s The lowest frequency at which...
  49. K

    Wave constructive and/or destructive interference question

    Homework Statement https://portal.utoronto.ca/courses/1/Fall-2014-PHY100H5-F-LEC0101/ppg/quiz%2061016132114/f1q2g1.jpg The figure shows two sets of water waves, created by two sources labeled "A" and "B." The solid half-circles represent wave crests from A, and the dashed half-circles...
  50. K

    Constructive or destructive interference after a set number of waves?

    Homework Statement Two sources, S1 and S2, send our circular waves that are in phase and of the same frequency. They have the same wavelength (0,5m) and the same amplitude. Will there be a maxima og a minima at the given points: a) S1P = 5.00 m og S2P = 6.50 m? b) S1P = 5.00 m og S2P =...