What is Diffraction: Definition and 1000 Discussions

Diffraction refers to various phenomena that occur when a wave encounters an obstacle or opening. It is defined as the bending of waves around the corners of an obstacle or through an aperture into the region of geometrical shadow of the obstacle/aperture. The diffracting object or aperture effectively becomes a secondary source of the propagating wave. Italian scientist Francesco Maria Grimaldi coined the word diffraction and was the first to record accurate observations of the phenomenon in 1660.

In classical physics, the diffraction phenomenon is described by the Huygens–Fresnel principle that treats each point in a propagating wavefront as a collection of individual spherical wavelets. The characteristic bending pattern is most pronounced when a wave from a coherent source (such as a laser) encounters a slit/aperture that is comparable in size to its wavelength, as shown in the inserted image. This is due to the addition, or interference, of different points on the wavefront (or, equivalently, each wavelet) that travel by paths of different lengths to the registering surface. However, if there are multiple, closely spaced openings, a complex pattern of varying intensity can result.
These effects also occur when a light wave travels through a medium with a varying refractive index, or when a sound wave travels through a medium with varying acoustic impedance – all waves diffract, including gravitational waves, water waves, and other electromagnetic waves such as X-rays and radio waves. Furthermore, quantum mechanics also demonstrates that matter possesses wave-like properties, and hence, undergoes diffraction (which is measurable at subatomic to molecular levels).

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  1. M

    Fourier transforms, convolution, and Fraunhofer diffraction

    I've been exposed to this notion in multiple classes (namely math and physics) but can't find any details about how one would actually calculate something using this principle: Diffraction in optics is closely related to Fourier transforms and finding the Fraunhofer diffraction of an aperture...
  2. J

    MHB Calcite X-Ray Diffraction: Find Smallest Angle

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  3. ChrisXenon

    What is the Fundamental Reason for EMR Diffraction?

    I know the textbook definitions and descriptions of the phenomenon, but I'm hoping for a fundamental WHY. I can see that when a water wave passes an obstacle, the wave spreads out into that object's shadow because the wave's energy is not constrained to any direction and so it will move out in...
  4. Sandeep T S

    I Diffraction experiments with one particle at a time?

    Is anyone did experiment on diffraction with single particle at a time? Do they get diffraction pattern? I referred particle as both electron and photon And I want to know any experiment( classical, or single particle at time) don't show any diffraction pattern in single slit experiment.
  5. DariusP

    Varying thickness diffraction grating

    I know that a plane wave going through a slit becomes a spherical wave because of a Huygens-Fresnel principle. Can someone explain to me why a plane wave splits into many plane waves with different directions when going through a plate with varying thickness? Can someone explain me this image?
  6. T

    Deriving circular aperture diffraction

    Homework Statement i don't understand where the 1.22 number comes from like in ## sin \theta = 1.22 \lambda /D ## so i tried to derive but to not much help Homework Equations electric field at distance R due to slit of length D is ## E = \frac{\epsilon_l D}{R} sinc(\frac{kD}{2}sin \theta)sin(wt...
  7. F

    A Fresnel Diffraction - Opaque Barrier Question

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  8. M

    Building a half-mile long photogate and fighting diffraction

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  9. G

    I The 1.22 factor in the angular resolution

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  10. negative

    I Diffracted photon/partice momentum

    when a single photon is supposed to form a diffraction pattern, they hit the detector by different angles at the slit. so then what cancels this photon's momentum change? what happens to the photon's energy/frequency?what measurements has been done to confirm the answer?
  11. B

    I How to interpret the diffraction envelope

    Explanations of 2-slit interference sometimes show the interference pattern compared to a 1-slit diffraction pattern, and state that the latter represents a limit or envelope for the former. Is it correct to interpret the patterns as representing (directly or indirectly) the number of photons...
  12. zehkari

    Error Calculation for a Diffraction Grating's Performance

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  13. M

    I What are the patterns and formations seen in selected area diffraction?

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  14. S

    Diffraction Gratings: Calculating Wavelength for CD ROM

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  15. C

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  16. P

    The Difference Between Diffraction And Interference Patterns

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  17. S

    Fraunhofer diffraction pattern

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  18. Beth N

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  19. NihalRi

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  20. G

    A Fraunhofer's multiple slits versus atomic scatteres (diffraction theory)

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  21. Jeremy Feng

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  22. S

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  23. 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...
  24. Erickly

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  25. G

    A Diffraction on periodic Structures

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  26. F

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  27. C

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  28. S

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  29. ephphatha16

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  30. M

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  31. Clara Chung

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  32. M

    Diffraction Grating - Calculating Ruling Width

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  33. MermaidWonders

    MHB Solving for Slit Width-Wavelength Ratio at $\pm90°$ Diffraction Pattern

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  34. Buckethead

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  35. EF17xx

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  36. C

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  37. G

    Maximum Wavelength and Scattering Angle for Triangular Lattice

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  38. P

    I Minimizing diffraction in images using a photodetector

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  39. A

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  40. C

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  41. Paddyster

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  42. R

    Understanding Diffraction at a Single Slit: Notes and Resources

    [Mentors' note: This thread has been edited to change the level tag from 'A' to 'I'] Hello guys, I want the deduction part of- diffraction at single slit: Plz sent me the notes of this.
  43. Paddyster

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    Hi, I'm doing my third year project on diffraction gratings and patterns and analysaing them via computer software and Fourier transforms. I'm going to design my diffraction gratings this week and then create them via taking a picture with a disposable camera and using the negative film. What...
  44. Wrichik Basu

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  45. R

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  46. G

    Find ##2\theta## Values from Rotated Crystal and Intensity

    Homework Statement Consider the crystal in the attached image (https://ibb.co/ftMrBH) (a triangular lattice of white atoms with a triangular basis of grey atoms attached to them at angles of 0, 60 and 120. From a previous problem the fractional coordinates of the atoms in the basis are (0,0)...
  47. G

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  48. Pushoam

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  49. J

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  50. Paddyster

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