Why Does Light Diffract When Passing Through an Aperture?

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SUMMARY

Light diffracts when passing through an aperture due to its wave nature, a phenomenon well-documented since the 19th century. Key historical figures include Augustin-Jean Fresnel and Joseph von Fraunhofer, who contributed to the classical understanding of diffraction. Richard Feynman's book "QED" provides a modern quantum explanation, emphasizing that photons take paths with the least time to reach areas of higher probability. The discussion also highlights the significance of Huygens' Principle in understanding diffraction, although it is deemed incorrect by contemporary standards.

PREREQUISITES
  • Basic understanding of wave-particle duality
  • Familiarity with Feynman's "QED" concepts
  • Knowledge of Huygens' Principle
  • Introduction to physics, including basic vectors and amplitudes
NEXT STEPS
  • Read Richard Feynman's "QED" for insights on quantum mechanics
  • Research Huygens' Principle for classical wave theory
  • Explore the works of Fresnel and Fraunhofer on diffraction
  • Study the implications of wave-particle duality in modern physics
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Students of physics, educators teaching optics, and anyone interested in the fundamental principles of light behavior and quantum mechanics.

AlanPartr
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I was wondering if anyone knew why light (or any other particles) diffracts when it goes through an aperture?
 
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This is due to the wave nature of light. It is was well documented in the 19th century. You may wish to research the work of Fresnel and Fraunhofer for the classical presentation.

For the particle aspect of it read QED by Richard Feynman.
 
THe quantum explanation is currently the best explanation, and for that you would need to read Feynman's "QED" (it's a thin book that takes a long time to read). BUt before reading this book, you need a full-year of introduction to physics, including basic vectors (vector arrows are used when analyzing photons, but they are called "amplitudes" which actually means "probability.")

The best thing about Feynman's QED is that the same explanation also explains refraction, reflection and interference. This is the kind of simplification that Physics is all about.

In an undeniably insufficient explanation:
Photons will take a certain path that will require the least amount of time to reach a point at which there is a greater-than-zero probability of existing there. Due to the nature of all the possible paths for the photon, there will be points of higher and lower probability (that the photon will be there) Bright diffraction "fringes" indicate zones of high probability and dark "fringes" indicate regions of near zero probability.

IF you want the old explanation of "why diffraction of light" then you must follow the wave model. Do a google search for "Huygens' Principle." It's not easy either, and it's also incorrect for light (according to our current, most accepted explanation).
 
Dang it!

Why can't I ever get the first word in?
 
It is reassuring that we all posted the same reference! :smile:
 
cheers

cheers

looks like I've got some reading to do
 
Originally posted by Ambitwistor
I don't want to scare Alan off ... Feynman's book was based off of lectures intended for laymen, and I think you can absorb a great deal from it without prior exposure to physics or vectors.

You only need to read the first two chapters (of four).
My 16/17 year old Physics students are all told to read it - they cope (just about), so don't be put off Alan. It is a very good book.
 

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