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Diffraction of a circular aperture

  • Thread starter groosagi
  • Start date
  • #1
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Homework Statement


A collimated laser beam ( λ=600 nm) having an intensity I=10 W/m2 is incident
perpendicularly on an opaque screen containing a circular hole with diameter
D=3.6 mm. Calculate the intensity at a point on the central axis that is distanced
180 cm from the screen.


Homework Equations



I=4I0[tex]\left([/tex][tex]\frac{J(kaq/R)}{(ka/R)}[/tex])^2

The Attempt at a Solution



firstly I am confused if i should treat this as Fraunhofer or Fresnel diffraction. I know that for a circular aperture it will form an airy disk, but that will leave the bessel function = 0, which means the resulting intensity is zero. (that would make sense if the center is dark, ut it should be bright.

I really think I am missing something simple here. please help.
 

Answers and Replies

  • #2
ehild
Homework Helper
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1,813
It is true that the J1(x) Bessel function is zero at x=0, but J1(x)/x has a finite limit.

ehild
 

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