Talk:Fraunhofer diffraction

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I keep getting contradictions on Wikipedia:

This page:

"...exceeding that defined as fresnel diffraction (F >> 1)"

"...any wave which has a fresnel number of larger than one -- F >> 1, is therefore subject to Fraunhofer diffraction"

Fresnel diffraction:

"Fresnel diffraction or near-field diffraction is the diffraction pattern of an electromagnetic wave obtained close to the diffracting object (often a source or aperture). More accurately, it is the diffraction case when the Fresnel number is large and thus the Fraunhofer approximation (diffraction of parallel beams) can not be used."

Fresnel number:

"Depending on the value of F the diffraction theory can be simplified into two special cases:

  • Fresnel diffraction for F <or= 1
  • Fraunhofer diffraction for F >> 1"

Having just done experiments on Fraunhofer diffraction I was pretty sure it occurs when L is large, which makes the Fresnel number small, ie F < 1 , however I was pretty confused about the topic. I'd appreciate it if someone could clear this up a bit? This is probably the first time when Wikipedia has made me even more confused.

Contents

[edit] Apologies

Apologies, i wrote the fresnel case in here. Cheers for changing it over; i didn't notice until i came back just now. J O R D A N [talk ] 12:39, 7 February 2007 (UTC)

[edit] History?

The history of the wave theory of light refers mostly to Grimaldi, Huygens, Young and Fresnel. However we call single slit diffraction "Fraunhofer diffraction". I have looked through Fraunhofer article on wikipedia but I fail to see where Fraunhofer fits in the history of diffraction and what he did to deserve the honor of having single slit diffraction named after him. —The preceding unsigned comment was added by Pboudreau (talk • contribs) 23:44, 22 April 2007 (UTC).

Well, Fraunhofer did create the diffraction grating for the first accurate spectroscopy. It's reasonable to assume he observed Fraunhofer diffraction in sharp spectral lines (you pass the light through a slit before shining it on the diffraction grating) and found that the same far-field math can explain both phenomena. That's all a guess, though. — Laura Scudder ☎ 03:11, 23 April 2007 (UTC)

[edit] How can an aperture have a gaussian profile?

Please, enlighten me. 129.173.133.235 13:48, 30 October 2007 (UTC)

For example a dia film with a transmittance varying with position. Han-Kwang (t) 17:20, 30 October 2007 (UTC)

[edit] Change over to Goodman

I think the treatment of Fraunhofer diffraction is much more understandable using the methods of Fourier analysis. The fourier treatment in Goodman is excelent. I plan on switching this article over to proper analysis in the near future. Gfutia (talk) 18:12, 13 March 2008 (UTC)

I agree that the content needs some updating. Like it is now, the explanation sounds a bit 19th century. I believe less importance should be put on slits and apertures. Fraunhoffer diffraction occurs with any wavefield distribution, not only these simple binary masks. According to me, the Fourier transform property should be mentioned in the very first paragraph.Pierre T. (talk) 21:23, 17 March 2008 (UTC)
I added the Fraunhofer formula from Goodman. I know it's not explained at all, but I just wanted to get it in there. I'm a graduate student taking a course in Fourier Optics, something that largely discusses the Frunhofer regime. Time permitting, I'm going to try to update this article to make it more accessible. Gfutia (talk) 03:29, 24 March 2008 (UTC)