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Fresnel diffraction at F>1??

On the page on diffraction, it says that fresnel diffraction is the more general case, which leads me to think that there is no F at which fresnel diffraction is more or less accurate. In other words, I'm saying fresnel diffraction can be used when F is anything, not just greater than one. Is this right? Fresheneesz 05:44, 20 March 2006 (UTC)[reply]

Nevermind.. Fresnel diffraction should be used when F is largeish. But this leaves out a bit of fresnel numbers. What if your F is .98 ? what then? Is there more accurate and general ways of determining diffraction? Fresheneesz 05:50, 20 March 2006 (UTC)[reply]

reply: For large L then the case will be Fraunhofer. Therefore Fraunhofer is valid for values of F less than 1.

Fresnel number definition

As far as I know, the given definition of Fresnel number is valid for the radius and not the diameter of the diffracting aperture. For the diameter you will have : F=(D/2)^2/(lambda*R

Fresnel number derivation

Does anyone have a source on how this equation was derived? My Fourier Optics (Goodman) text pg 85 simply defines Fresnal number as it is defined here without explanation.Mollynet (talk) 01:43, 4 December 2009 (UTC)[reply]

@@ Line 11: / Line 11: @@
 As far as I know, the given definition of Fresnel number is valid for the radius and not the diameter of the diffracting aperture.
 For the diameter you will have : F=(D/2)^2/(lambda*R
+==Fresnel number derivation==
+Does anyone have a source on how this equation was derived?  My Fourier Optics (Goodman) text pg 85 simply defines Fresnal number as it is defined here without explanation.[[User:Mollynet|Mollynet]] ([[User talk:Mollynet|talk]]) 01:43, 4 December 2009 (UTC)