- The displayed diffraction pattern
measures 30 cm X 30 cm.
- Note the relatively small aperture
is what gives rise to the big
diffraction pattern.
But it is NOT a very
small aperture.
The ratio of
wavelength to
aperture size scale is 0.663/20 = 0.03315.
So ∼1.5 orders of magnitude
less than 1 which is smallish, but still NOT tiny.
So one gets a noticeable diffraction pattern.
- If the aperture
were progressively scaled up, the central bright fringe
would expand into a big square beam of light
that would be practically an image
of the aperture.
The interference fringes
would would narrow down into near invisibility becoming
very faint, except very near the bright central fringe.
With reflections and other sources of light, the
interference fringes
would be washed away.
- The particular shape of the
diffraction pattern
is a result of the square
aperture.
Different apertures would give different shapes.
A circular aperture would give
a diffraction pattern with
circular symmetry
(which is called an Airy diffraction pattern)
as it must since there is nothing in the
aperture to break
circular symmetry.
- Further elucidation is provided by the
Young's Double Slit Experiment | 1:09
video below.
php require("/home/jeffery/public_html/astro/electromagnetic_radiation/diffraction_videos.html");?>
Credit/Permission: