I Can't Get No Less Diffraction ...

Started Mar 18, 2013 | Discussions thread
wfektar Contributing Member • Posts: 700
Re: Addendum: I Can't Get No Airy Action ...

Detail Man wrote:


While that was my original question, too, several sources seem to confirm this statement by Frans:

I lack the physics background to explain this properly, but it is squared because we are dealing with incoherent light, which is a safe assumption for typical photographic light sources. Coherent light sources, such as lasers, will have a sinc(x) diffraction pattern upon passing through a narrow slit.


The sinc function is just the FT of a tophat. Don't muddy the waters with incoherent vs coherent.

... and thus it is the "intensity" (the square of the electromagnetic field strength in units of Volts/Meter, itself in units of Joules/Meter^2) seems to be what is used in these types of analyses.

We can't measure the field at optical frequencies -- it cycle averages to zero. We can measure the energy, which goes as the modulus square of the field, so that's where the square comes from.

Post (hide subjects) Posted by
Keyboard shortcuts:
FForum PPrevious NNext WNext unread UUpvote SSubscribe RReply QQuote BBookmark MMy threads
Color scheme? Blue / Yellow