What is Interference and diffraction: Definition and 50 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

    B Explanation for bright fringes in Single Slit Diffraction

    In Young's Double Slit Experiment, we were shown the complete derivation for location of fringes, width of fringes etc. on interference by two point sources of light and all was well. In Single Slit Diffraction we were just asked to remember the formulae as they were with little explanation. I...
  2. G

    A Diffraction from a set of concentric rings with random phase

    I have been considering the properties of a Diffractive Optical Element (DOE) consisting of a very large number of concentric rings of equal (small) width, where the thicknessses of the rings are such as to produce random phase shifts in the range 0 to 2pi. I think I understand the behaviour of...
  3. jerry222

    Interference of light in thin films

    Phase difference is $\phi=\frac{2pi}{\lambda}* \Delta+\pi$ Phase difference, max: $\Delta \phi=2pim=\frac{2pi}{\lamda_{max}}*2nd$ Phase difference, max: $\Delta \phi=2pim=\frac{2pi}{\lamda_{min}}*2nd+pi$ Flim thickness: $d=100nm$ Set the equations equal to each other i got a d=-100nm which...
  4. Dyn Doeth

    A Structural coloration of a zeolite monolayer

    I have a monolayer of zeolite crystals on glass with the thickness of the zeolites about 800nm. When I look at the reflection of fluorescent light bulbs on this monolayer, the reflection is white except at specific angles. At around 45 deg, the colour appears red/magenta and at a lower angle...
  5. P

    To find the resultant intensity

    So I thought of calculating the path differences between all the 3 points by taking them in pairs of 2. S1 and S2 S2 and S3 S3 and S1 I got the path differences as λ/3 , λ and 2λ/3 I can now find their phase differences using the equation Cosx=2π/λ* (path difference) Then I can apply the...
  6. David Charles

    I Double Slit Interference Question II

    A stream of photons pass through a double-slit. The photon stream emerging from each slit then passes through a crystal which splits each photon into coherent entangled pairs. One photon from each pair heads towards a detector (D0) that "can be scanned by a step motor along its x-axis for the...
  7. David Charles

    I Double Slit Interference Question

    A laser provides a constant stream of photons which pass through a double-slit. The photon stream emerging from each slit then passes through a crystal which splits each photon into coherent entangled pairs. One photon from each pair heads towards a photosensitive screen and the entangled twin...
  8. A

    What do these submaxima represent - Interference Pattern

    Hey all, Here's a neat picture: The green arrow points towards one of the submaxima that I am curious about. It's the submaximum of the curve labeled 1. 1. represents the interference pattern 3. represents the diffraction pattern 2. represents the irradiance pattern I guess that those...
  9. Marco Masi

    I Double slit displaying anti-fringes?

    The conventional Young double slit experiment displays the interference fringes with the first intensity maxima at the center of the detection screen ('center' means aligned with the center between two slits of equal aperture). These are simply called 'fringes'. However, I'm wondering if and how...
  10. Y

    Interference Fringes in a Diffraction envelope

    Homework Statement My question is at https://imgur.com/a/lDOUzjY . The de Broglie wavelength of the atoms in question is 45 pm. The distance from the slits to the detection plane is 1.95m. Each slit width is 1 micrometer. The distance between the slits is 8 micrometers. 2. Homework Equations...
  11. Erickly

    Film Thickness for Minimum Reflection of Monochromatic Light: How to Calculate?

    Homework Statement Monochromatic light of wavelength, λ is traveling in air. The light then strikes a thin film having an index of refraction n1 that is coating a material having an index of refraction n2. If n2 is larger than n1, what minimum film thickness will result in minimum reflection of...
  12. S

    Young's double slit experiment green laser

    Homework Statement If a green laser is (wavelength = 532nm) sent through two slits with a separation of 127 um, how wide (in total) would the 11 green dots formed be if they were projected onto a screen 1.25m away from the slits? Refer to this diagram sorry for bad quality...
  13. PumpkinCougar95

    B Young's Double slit experiment with different slit sizes

    What would happen if a youngs double slit experiment is done with different slit sizes? I get the feeling that the intensity might never be zero as the waves might never cancel out completely. Am I right? How should I analyse the Intensity? Would I have to do something like what is done while...
  14. C

    More slits, farther maxima of interference patterns, why?

    When observing interference patterns, one will notice that the maxima from a double slit are more intense and farther apart than the maxima of a single slit. Likewise, the maxima from a diffraction grating are more intense and farther apart than maxima of a double slit. Why is this? I...
  15. C

    Interference of light, emission spectroscopy prac. report

    Ok, so I've got a practical report due tomorrow and I just wanted to clarify a few things. A bit of background knowledge first. The practical involved taking angular measurements for the emission lines of the Mercury spectrum using the apparatus, a spectrometer and a Mercury spectral tube...
  16. Z

    Investigation about the emission spectrum of Mercury

    Homework Statement For our investigation, we used a diffraction grating spectrometer to observe the emission spectrum of mercury. We conducted the experiment in a pitch black room to avoid any unwanted light pollution, etc. Whilst conducting the experiment we observed a number of 'faint' lines...
  17. N

    Double slit experiment with a glass-covered slit of unknown n

    Homework Statement A double-slit experiment uses a helium-neon laser with a wavelength of 633 nm and a slit separation of 12mm. When a thin sheet of glass is placed in front of one of the slits, the interference pattern shifts by 5 fringes. When the experiment is repeated under water, the shift...
  18. nso09

    Three slit minima and maxima and path differences

    Homework Statement Find at which angles θ the interference picture that appears on a distant screen made by three thin slits separated by distance d and enlightened by a source of wavelength λ (see figure) a) Shows its maxima. b) Shows its minima. multiple slit diffraction, d, ##\lambda##...
  19. nso09

    Relationship of slit, wavelength, and intensity

    Homework Statement Coherent electromagnetic radiation is sent through a slit of width 0.01 mm. For which of the following wavelengths will there be no points in the diffraction pattern where the intensity is zero? A. Blue light of wavelength ##\lambda=500 nm## B. Infrared light of wavelength...
  20. nso09

    Interference on a mirror -- waves confusion

    Homework Statement ##d=0.52 cm,## ##\lambda=431nm##, ##L=119 m## Homework Equations ##dsin\theta=(m+1/2)\lambda## for constructive/bright fringes since there is a pi shift already The Attempt at a Solution a) $$sin\theta\leq1$$ $$(.0052/431e-9)-0.5=m=12064$$ 2 \e{3} $$ total bright fringes =...
  21. Gigi777

    Why does diffracted white light have a white central fringe?

    Hey everybody, Homework Statement : [/B] I came across a question discussing Young's Double Slit interference and was wondering how come when we diffract white light through the slits it gives us a central antinodal fringe that is also white? The question itself came in parts firstly...
  22. A

    What do interference and diffraction have in common

    Homework Statement What do interference and diffraction have in common? We are learning the sound waves, but I would like to know all the things they have in common. Homework Equations x2-x1=λ/2 (contructive) 3. The Attempt at a Solution The waves have the same frequency, after the process...
  23. Willfrid Somogyi

    I Highest Order Diffraction Ring

    So we have the standard diffraction equation for crystals, being: nλ = 2dsinθ. If we keep the wavelength and the lattice parameter the same then n simply depends on θ. So there must be a maximum order diffraction ring that you could obtain as once you get to 90° you're essentially going in the...
  24. NatFex

    Distance between fringes in an interference pattern?

    For the sake of simplicity let's suppose I'm talking about the diffraction of light through one slit. Are the distances between any two consecutive fringes (apart from the central maximum) exactly equal? Assuming the wavelength, slit width, and distance between slit and screen do not change...
  25. M

    Interference of light Intensity

    An Interference pattern is produced by light of wavelength 490nm from a distant source incident on two identical parallel slits separated by a distance (between centers) of d=0.630mm. a) If the slits were very narrow what would be the angular position theta1 and theta2 of the first and second...
  26. A

    Optics : interference and diffraction

    interference is a superposition of two waves coming two slits... diffraction is a superposition of a family of waves from a single slit.. then how the fringes formed during double slit experiment is actually a superposition of single-slit diffraction from each slit and the double-slit...
  27. A

    Why Don't Spherical Waves Interfere: Exploring Huygens Principle

    Hi according to Huygens principle every point on the wave front acts as a spherical source. so if a we emit monochromatic light on a screen without passing light from grating, we should see interference pattern but we don't. why don't these spherical waves interfere with each other? is this...
  28. kelvin490

    How Holography Works: Explained

    To make a hologram a film is exposed to an incident plane wave and wave from the object to record the interference pattern on the film. The principle is commonly explained in a way like that in p.1212 of "University Physics" (...
  29. kelvin490

    X-Ray Diffraction in Crystals: Exploring Scattering & Interference

    In explaining x-ray diffraction of crystals, usually the approach is to consider the atoms absorb radiation and scatter it, at some angles constructive interference occur and bright spots can be observed. It seems that it is different from the diffraction of slits or gratings because in these...
  30. kelvin490

    Question about dark fringe in diffraction

    In finding the angle for the mth dark fringe of single slit diffraction using Huygen's principle, they usually split the slit into equal portions. For example, to find the first dark fringe the slit is split into two equal spacings and if the path difference between the edge and the middle point...
  31. S

    Double slit over time, single slit in moment

    What happen if you do the following version of the double slit experiment: In first sequence the right slit is open and the left is closed, and a number of electrons are sent through. Then the right slit is closed and the left is opened, and a new sequece of electrons are fired. After completing...
  32. C

    Young's Double-slit Experiment

    Homework Statement In a KhanAcademy video, light of wavelength 700nm shines through a double-slit whose holes are spaced 1300nm apart. If a screen is placed 3m away from the double-slit, what will be the distance from the central bright spot on the screen to the next bright spot...
  33. P

    Interference and Diffraction

    Homework Statement Write down the intensity equation for a two-slit interference pattern with diffraction effects included. Indicate which part originates from double-slit interference and which part from single-slit diffraction. What happens when the angle = 0Homework Equations...
  34. 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...
  35. I

    Help me understand interference and diffraction better

    Homework Statement I've been reading a book about waves. I skipped the test earlier this year because I had not done any problems and thought it would be a waste of time to try. But now I kind of have to do it, I've re-read the book but it's much to understand and remember. Especially the...
  36. M

    Difference Between Interference and Diffraction

    Can anyone tell me the difference between interference in double slit's and single slit diffraction?
  37. 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...
  38. 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...
  39. O

    Interference and Diffraction: Coating on a Lens to Minimize Reflection

    Homework Statement What is the minimum thickness of coating which should be placed on a lens in order to minimize reflection of 661 nm light? The index of refraction of the coating material is 1.40 and the index of the glass is 1.65. Hint: You must take into account the 180 degree...
  40. 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...
  41. 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
  42. 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...
  43. D

    What energies are needed to observe interference maxima in a crystal?

    A certain crystal has a planar spacing of .25nm. What energies are necessary to observe up to three interference (diffraction) maxima for a)electrons and b)neutrons?
  44. A

    How Much Did the Mirror Move in a Michelson Interferometer Experiment?

    Homework Statement The distance between the movable mirror and the beam splitter in a Michelson interferometer is increased a small amount. What this happens, you see 200 dark fringes move across the field of view. If the incident light was 600nm, by how much was the mirror moved (in...
  45. T

    Wave optics interference and diffraction

    Imagine you are trying to measure the width of a single strand of spider web. You have fastened the web to the slide, only rather than mounting the strand vertically as you did with the hair, you have mounted it horizontally. You illuminate the strand with a 650nm laser and project the resulting...
  46. P

    Calculating Intensity at a Point in a Diffraction Pattern

    I have the follwoing question for prep for a lab, i have tried to work out the answer but i am struck with trying to work out the intensity at a certain point, in this case 4.1mm from the central maximum. I have tried using trig to calculate the angle to the point using trig then using...
  47. C

    Interference and Diffraction of Light

    I didnt go to school today, and so missed day of class, now i all lost someone help. White light is incident normal to the surface of the film as shown below. It is observed that at a point where the light is incident on the film, light reflected from the surface appears green (lamda = 525...
  48. N

    Two slit interference and diffraction

    why is it better to use red light , instead of blue or white light, for 2 slit interference and diffraction measurements?
  49. C

    Interference and diffraction of light

    Why is it impossible to observe an interference pattern from two adjacent incandescent globes? What is meant by coherant light- and how would you describe two ways of producing it?
  50. tandoorichicken

    Solving Interference and Diffraction Problems

    I know how to do these, I think I just somehow fudged up the calculations: 1)A pair of narrow slits is illuminated with red light of wavelength \lambda = 633 nm. The slits are separated by 0.10 mm center-to-center. (a) What is the angular separation of the interference maxima near the center...