The intensity pattern of diffraction (function of theta) from a point source
through a round aperture is the square of a 1st order Bessel function of the
first kind of a function of theta & lamda, all divided by the same function
of theta & lamda.
~ [pi * r^2 * J(f(theta, lamda)) / f(theta, lamda)]^2
where:
J(x) is the 1st order Bessel function of the first kind of x, and
f(theta, lamda) = 2 * pi * r * sin(theta) / lamda, and
r is the radius of the aperture, and
lamda is the wavelength.
This function looks very much like the old familiar sin(x) / x pattern,
squared.
Regards,
Bob...
--------------------------------------------
"Do not suppose that abuses are eliminated by destroying
the object which is abused. Men can go wrong with wine
and women. Shall we then prohibit and abolish women?"
-Martin Luther
From: "Chris" nimbo@ukonline.co.uk
> There will also be a diffraction effect because of the difference of path
> length across the pinhole and the wavelength of light. I can't remember
the
> answer but you have to integrate the light arriving at a point from across
> the pinhole and it makes a difference as it is circular. I will try to do
> the integration shortly but if I remember correctly there is a term
> (theta)/sin(theta) in it somewhere.
>
