Why Does Light Diffract When Passing Through an Aperture?

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Discussion Overview

The discussion revolves around the phenomenon of light diffraction when passing through an aperture, exploring both wave and quantum explanations. Participants reference historical and contemporary theories, as well as educational resources related to the topic.

Discussion Character

  • Exploratory
  • Technical explanation
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • Some participants suggest that light diffraction is explained by the wave nature of light, referencing the works of Fresnel and Fraunhofer.
  • Others argue that the quantum explanation, particularly as presented in Feynman's "QED," is currently the best understanding of the phenomenon.
  • A participant notes that understanding Feynman's explanation requires prior knowledge of basic physics concepts, including vectors and probability amplitudes.
  • One participant mentions that diffraction patterns can be interpreted as zones of varying probability for photon presence, with bright fringes indicating higher probability and dark fringes indicating lower probability.
  • There is a suggestion to explore Huygens' Principle for a classical wave model explanation, though it is noted that this may not fully align with current understanding of light behavior.
  • Several participants express a shared appreciation for Feynman's work, indicating its accessibility and educational value.

Areas of Agreement / Disagreement

Participants express differing views on whether the wave model or the quantum model provides a better explanation for diffraction. There is no consensus on a singular explanation, and the discussion remains open to multiple interpretations.

Contextual Notes

Some limitations include the need for foundational knowledge in physics to fully grasp the quantum explanation, and the potential inadequacy of classical models in explaining light behavior according to current theories.

Who May Find This Useful

This discussion may be of interest to students and educators in physics, as well as individuals curious about the fundamental principles of light behavior and diffraction.

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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