Physics Help Forum Diameter and radius of central bright

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 Nov 8th 2018, 12:31 AM #1 Senior Member   Join Date: Mar 2009 Location: Yadupatti Bazar,Sitamarhi Posts: 133 Diameter and radius of central bright I have read two different value in diffraction pattern. One is angular radius of central bright is given 1.22 lamda/D Other is diameter of central bright is kanda/D. Which one is correct. ? __________________ If science solves one problem, it creates ten other problems.
 Nov 8th 2018, 02:28 AM #2 Senior Member     Join Date: Jun 2016 Location: England Posts: 640 What is "kanda"? does perhaps kanda=1.22 lamda? __________________ ~\o/~
Nov 8th 2018, 03:16 AM   #3
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 Originally Posted by Woody What is "kanda"? does perhaps kanda=1.22 lamda?
Yeah, it's lambda.

It depends what you are talking about. The value $\displaystyle 1.22 \lambda$ is the distance to the first minimum from the centre of an Airy disk.

If you have some other pattern, you might instead have a different formula.

 Nov 8th 2018, 04:19 AM #4 Senior Member   Join Date: Mar 2009 Location: Yadupatti Bazar,Sitamarhi Posts: 133 Yes. That is lamda.. In case of diffraction from circular aperture radius of central bright is given as 1.22 lamda/D In case of fresnel calculation diffraction from circular aperture diameter is given as kanda/D ....How? __________________ If science solves one problem, it creates ten other problems.
 Nov 8th 2018, 06:37 AM #5 Senior Member   Join Date: Aug 2010 Posts: 369 If "kanda" was simply a misprint for "lambda", why do you keep writing it?