On Saturday, Nov 1, 2003, at 12:32 Bernard Cleyet wrote:
> try replacing the card with a strip whose
> depth is the same as its width.
I am not performing an experiment. Why would the
length of the card slip (which divides a beam from
a pinhole into two separate parts) have to play a
role? I suppose the slip card was black in order to
minimize stray light. What is wrong with thinking that
the card should act as if it were a wire?
Unfortunately, I was not able to figure out what
fraction of the beam area was actually covered by
the card. There were no illustrations in Young's
paper. To act as a single slit each uncovered area
was probably very narrow. Thus the slip card
shadow was probably at least 90% of the area of
the diverging beam.
In a single-wire experiment the situation is usually
opposite; the area of the wire is a small part of the
beam area. I can not prove it but I suspect that in
going from one extreme to another one must be able
to observe a transition from "peaks of equal widths"
to a typical diffraction pattern -- a "central strong
peak about twice as wide as other (weaker) peaks."
That may be an experiment worth performing.
Ludwik Kowalski