What is Double slit diffraction: Definition and 22 Discussions

In modern physics, the double-slit experiment is a demonstration that light and matter can display characteristics of both classically defined waves and particles; moreover, it displays the fundamentally probabilistic nature of quantum mechanical phenomena. This type of experiment was first performed, using light, by Thomas Young in 1801, as a demonstration of the wave behavior of light. At that time it was thought that light consisted of either waves or particles. With the beginning of modern physics, about a hundred years later, it was realized that light could in fact show behavior characteristic of both waves and particles. In 1927, Davisson and Germer demonstrated that electrons show the same behavior, which was later extended to atoms and molecules. Thomas Young's experiment with light was part of classical physics long before the development of quantum mechanics and the concept of wave-particle duality. He believed it demonstrated that the wave theory of light was correct, and his experiment is sometimes referred to as Young's experiment or Young's slits.

The experiment belongs to a general class of "double path" experiments, in which a wave is split into two separate waves that later combine into a single wave. Changes in the path-lengths of both waves result in a phase shift, creating an interference pattern. Another version is the Mach–Zehnder interferometer, which splits the beam with a beam splitter.In the basic version of this experiment, a coherent light source, such as a laser beam, illuminates a plate pierced by two parallel slits, and the light passing through the slits is observed on a screen behind the plate. The wave nature of light causes the light waves passing through the two slits to interfere, producing bright and dark bands on the screen – a result that would not be expected if light consisted of classical particles. However, the light is always found to be absorbed at the screen at discrete points, as individual particles (not waves); the interference pattern appears via the varying density of these particle hits on the screen. Furthermore, versions of the experiment that include detectors at the slits find that each detected photon passes through one slit (as would a classical particle), and not through both slits (as would a wave). However, such experiments demonstrate that particles do not form the interference pattern if one detects which slit they pass through. These results demonstrate the principle of wave–particle duality.Other atomic-scale entities, such as electrons, are found to exhibit the same behavior when fired towards a double slit. Additionally, the detection of individual discrete impacts is observed to be inherently probabilistic, which is inexplicable using classical mechanics.The experiment can be done with entities much larger than electrons and photons, although it becomes more difficult as size increases. The largest entities for which the double-slit experiment has been performed were molecules that each comprised 2000 atoms (whose total mass was 25,000 atomic mass units).The double-slit experiment (and its variations) has become a classic for its clarity in expressing the central puzzles of quantum mechanics. Because it demonstrates the fundamental limitation of the ability of the observer to predict experimental results, Richard Feynman called it "a phenomenon which is impossible […] to explain in any classical way, and which has in it the heart of quantum mechanics. In reality, it contains the only mystery [of quantum mechanics]."

View More On Wikipedia.org
  1. ab200

    Double Slit Diffraction with Angled Light

    Given that [y][/m] is equal to the position of the interference maxima and is the variable I’m solving for. I got as far as setting up two expressions, one for sinθ and the other for tanθ. sinθ = (mλ)/d tanθ = ym/L My first instinct was to set θ = 40 degrees. By relating sinθ and tanθ to each...
  2. S

    Double Slit Wave Interference - what is m?

    Hi, I'm doing a very simple problem, but I don't understand the diagram provided (see image below). What is m here? I know that m is the order with respect to the central bright fringe, but there isn't a central bright fringe (assuming those circles are the bright fringes)? Homework...
  3. 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...
  4. CricK0es

    What is the missing variable in the double slit interference pattern?

    Homework Statement Laser light of wavelength 517 nm illuminates two identical slits, producing an interference pattern on a screen 87.5 cm from the slits. The bright bands are 1.15 cm apart, and the third bright bands on either side of the central maximum are missing in the pattern. a.) Find...
  5. Arget

    Double slit diffraction ripple

    Consider diffraction in a ripple tank from two narrow slits. Answer true (T) or false (F) for each of the following statements. E.g., if the first statement is true and the rest false, enter TFFF. You have 6 tries. If the frequency of the wave source is halved, then the angle between the...
  6. B

    Hopelessly Confused (Strange Light Distribution)

    I'm not quite sure how to describe this phenomena but in my town we have a large boardwalk structure and it is closed off almost entirely underneath by a sea wall. this leaves slits on top with the boards and slits near the top of the sea wall where a concrete beam will pass through. at certain...
  7. N

    Making a program to model the Double Slit Experiment?

    Hey guys the Idea of simulating the DSE with a program caught my interest but I just had a few questions regarding the DSE Is there a function that models the probability of finding an electron at a certain point ONCE It's BEEN FIRED FROM AN ELECTRON GUN? like an amplitude function squared or...
  8. spitonem

    Double Slit Diffraction Problem

    I had this problem on my exam and I was pretty sure i knew what to do but it couldn't come up with the right answers. I diagrammed the problem and showed the way i tried to solve it in blue. Can someone tell me where i went wrong? Basically i found the length the of the first maximum off the...
  9. L

    Meaning of Single Photon Interference Minima

    In the double slit experiment, when we send out one photon at a time, what does the appearance of minima in our interference pattern mean? When a single photon is fired, I understand (using "understand" very loosely) that the photon will interfere with itself. When this happens, does it still...
  10. T

    Difference between double slit diffraction and interference?

    Can somebody explain to me what is the difference between double slit diffraction and double slit interference?, to me they are the same thing but my teacher says they have two different meanings, thanks.
  11. A

    Intensity - Double slit diffraction

    Hello. I have been studying interference and diffraction and one doubt has appeared. When you consider the double slit experiment forgeting the effects of diffraction you get the following equation for intensity I^{}=4I_{0}cos^{2}(\frac{πdsin(θ)}{λ}) where d is the distance between the slits...
  12. D

    Uncertanty in double slit diffraction

    In a double-slit experiment electrons are sent through a doule slit where an indicator determines the slit each electron went through. These indicators tell the y coordinate to within d/2, where d is the distance between the slits. If this is the case show that the diffraction pattern will be...
  13. 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)...
  14. Z

    Double Slit Diffraction d/a

    Homework Statement (a) In a double-slit system, what value of d/a causes diffraction to eliminate the third bright side fringe? Homework Equations I(\theta) = I_mcos^2(\beta)(\frac{sin(\alpha)}{\alpha})^2 \beta =\frac{\pi d}{\lambda} sin \theta \alpha = \frac{\pi a}{\lambda} sin \theta...
  15. S

    Calculating Distance to Screen in Double Slit Diffraction Experiment

    Homework Statement Light of wavelength 460nm falls on two slits spaced .3 mm apart. What is the required distance from the slit to a screen if the spacing between the first and second dark fringes is to be 4mm?Homework Equations dsin(theta)=(m+1/2)lambda where d = .3mm y=4mm lambda = 460nm...
  16. E

    Single and double slit diffraction formulae

    Is the formula for single slit diffraction Dsin\theta = m\lambda identical to the double slit diffraction besides m being minima rather than maxima? More specifically will m + 1/2 tell me the angles between maxima?
  17. H

    Double slit diffraction maxima

    What effect does the distance between the two slits have on the intensity of the maxima?
  18. F

    Double Slit Diffraction fringes

    Homework Statement A parallel beam of mono-chromatic light (500nm) is incident on 2 long narrow slits: slit width is 0.1mm and the distance between slit centres is 0.3mm. a) How many bright fringes cover the central diffraction maximum? Homework Equations Condition for constructive...
  19. J

    Electron double slit diffraction with unequal widths

    Homework Statement Hey guys, I'm working on a problem with a double slit electron diffraction experiment. There is a beam of electrons shooting through two slits onto a screen. When only slit 1 is open, the number of electrons hitting the screen is 25 times the number of electrons hitting...
  20. S

    KE of Electrons to give same theta as light in double slit diffraction

    Homework Statement Coherent light is passed through two narrow slits whose separation is d. The second-order bright fringe in the interference pattern is located at an angle of theta. If electrons are used instead of light, what must the kinetic energy of the electrons be if they are to...
  21. N

    Deriving the formula for double slit diffraction as in Young from Fraunhofer

    Homework Statement I apologize for the blurriness in my title, I couldn't find anything better to fit within the length limit. The problem I'm stuck with, paraphrased, is to derive the formula for the diffraction pattern of a double slit, as found in the Young experiment, from the Fraunhofer...
  22. M

    Double Slit Diffraction Problem

    In a double-slit experiment it is found that blue light of wavelength 478 nm gives a second-order maximum at a certain location on the screen. What wavelength of visible light would have a minimum at the same location? ----- I have no clue how to approach this problem but looking in the...