Re: Thomas Young's experiment

[Ludwik Kowalski <kowalskil@MAIL.MONTCLAIR.EDU>]

On Thursday, Oct 30, 2003, at 22:02 US/Pacific, Bernard Cleyet wrote:

> He published it in the Philosophical Transactions of the Royal Society
> (London).
>
> http://www.pubs.royalsoc.ac.uk/phil_maths/news/interference.html
>
> The PT has an article on it.
>
> http://www.cavendishscience.org/phys/tyoung/tyoung.htm

Thanks, Bernard, for posting the URL to see the PT article.
It confirms what Hugh wrote about using the sun rather than
a flame. But it begs for a question. Suppose I decide to
perform the "split card" experiment with a sun beam.
Instead of using a card I would use a thin wire; it does not
need to be aligned "parallel with the beam." I would certainly
see fringes. And these could be presented as an argument
for the wave nature of light.

But would I be observing interference produced by light from
two coherent sources (the way Young's experiment is usually
described) or would I see a diffraction pattern due to a thin
wire? This question can be answered experimentally. In the
case of diffraction the central "fringe" is about two times
as wide as other fringes, in the double slit pattern all fringes
have about the same width.
Ludwik Kowalski