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. D

    Complementarity with single slit diffraction

    Sometimes I see complementarity explained as being not able to measure any wave and particle property at the same time. But it looks like in a standard double slit experiment the detector measures both particles as the interference, so the wave. The same with a single slit. If a photon is...
  2. D

    Diffraction condition - Kittel's Intro to Solid State Physics 8th ed.

    Homework Statement How to derive equation (22) on page 31 of Kittel's Intro to Solid State Physics 8th edition. The equation is: 2\vec{k}\cdot\vec{G}+G^2=0 Homework Equations The diffraction condition is given by \Delta\vec{k}=\vec{G} which from what I can surmise is the starting...
  3. P

    Does light bend around objects? (Not by gravity or diffraction)

    Today I was watching the full moon while I had one eye closed. There was a vertical metal rod which, by moving my head a bit, covered the moon completely, so that no direct light could hit my eye. (Yeah... I do things like that...) I saw a thin line of moonlight parallel to the rod right at the...
  4. C

    Sound diffraction around obstacles; low and high frequencies

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  5. C

    Bragg and Brillouin diffraction

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  6. D

    MHB Diffraction Grating: Uses, Light as Particle & When - 65 characters

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  7. F

    Path length difference and Diffraction

    Homework Statement A double slit experiment is set up using a helium-neon laser (wavelength 633 nm). Suppose we add a small piece of glass (n = 1.50) over one of the slits. Then, the central point on the screen is occupied by what had been the m = 10 dark fringe. Determine the thickness t of...
  8. I

    Problem with diffraction equations (diffraction and astrophysics)

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  9. P

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  10. Choisai

    Focused diffraction and Fourier transform

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  11. P

    Single Slit Diffraction effects

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  12. U

    Calculating Light Intensity in Diffraction Orders

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  13. H

    What is the concept behind Diffraction, n , Finding Dark/Bright Spots

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  14. F

    Diffraction Orders: Tilted Light Arrays & Incident Lights

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  15. T

    How to differentiate between refraction and diffraction of waves?

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  16. P

    Diffraction Grating problem (waves and optics)

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  17. R

    How does the wavelength of a water wave affect diffraction?

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  18. B

    Diffraction accompanied with photoelectric effect

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  19. A

    Simple positron diffraction problem

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  20. N

    How Does Diffraction Grating Reveal CD and DVD Storage Capacities?

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  21. H

    Diffraction Patterns: Does Distance Affect Diffraction?

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  22. B

    Diffraction pattern's dependency on wavelength

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  23. S

    Please help i cant understand anything about diffraction grating

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  24. T

    AP Physics B: Understanding Diffraction

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  25. S

    Single slit diffraction problem

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  26. U

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  27. D

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  28. S

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  29. I

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  30. A

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  31. S

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  32. H

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  33. U

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  34. G

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  35. S

    Confusion about the nature of Diffraction.

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  36. U

    How does the wavelength of light affect the radius of a diffraction disc?

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  37. S

    X-ray diffraction or reflection?

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  38. A

    Diffraction grating with monochromatic light vs. white light?

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  39. N

    Determine the angles between diffraction maxima

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  40. M

    Single slit double slit and diffraction grating

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  41. B

    Archived Lab Help: Find Miller Indices from Diffraction Pattern?

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  42. B

    Understanding Electron Diffraction: Heisenberg Uncertainty Principle

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  43. G

    Diffraction grating with slits out of phase

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  44. M

    Fraunhofer diffraction for a small obstracle

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  45. C

    How can diffraction occur with gap smaller than the wavelength?

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  46. M

    Diffraction grating experiment

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  47. J

    Bright Bands in Single Slit Diffraction

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  48. G

    Using diffraction slit as a lens

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  49. G

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  50. C

    Why does slit diffraction occur?

    Is it the same thing as Bragg diffraction, in the sense that it is caused by the photons being scattered in different directions when it hits the atoms of the solid material around the slit?
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