Exasperated, Bob Blakely tried one more time to explain sharp lines and edges, concluding thus: > If you do not understand this, there is no hope for you.
and Frantisek replied: > Bob, perhaps it's time for you to rehearse physics - light is a wave > as much as particle thing. Therefore, there is NO such thing as sharp > demarcation. ~PERIOD~. Look into any high-school physics book. Hi guys, If y'all keep pummeling Bob on this, I fear the Duchess will somehow get involved. ;-) <VBG> Actually, you're both sort of right, but I think you're arguing about two different scales of physical dimensions. It's true that at a sufficiently small scale of distances, there certainly are no sharp lines. It's all a quantum mechanical blur. But those dimensions are on the scale of the wavelength of visible light -- let's call it green (550 or so nanometers), since that's what our eyeballs are good at detecting. So, within about half a micron or so of what Bob's calling "the edge", things are blurred by the wave nature of light, as Frantisek points out. In this neighborhood, it's not a case of a photon "being there" or "not being there". Rather, it's a case of probabilities -- what we observe physically as diffraction. But I don't think Bob's talking about being half a micron from the edge. I think he's talking about distances more typical of MTF resolution targets. So doesn't he really mean distances more on the order of something like at least ten microns or so (which is about 100 LPM, if I did the arithmetic correctly)? As an aside, it's kind of cool that we'll only detect the wave nature of light if we set up an experiment to measure waves, and we'll only detect the particle nature of light if we set up an experiment to measure particles. See John Gribbin's "In Search of Schroedinger's Cat" for a good story about all of this stuff. Gribbin's a great writer. He not only makes comprehensible (for the general reader) the famous double-slit experiment, but he extends Schroedinger's particle-in-a-box thought experiment into an even more wacky thought experiment -- that is, can a cat sealed inside a box be both alive and dead at the same time? I'm sure Wheatfield Willie, being the cat fan that he is, has often asked himself this very question. ;-) http://www.amazon.com/exec/obidos/ASIN/0553342533/102-4181271-1671369 I can tell it's Friday again! Bill Peifer Rochester, NY - This message is from the Pentax-Discuss Mail List. To unsubscribe, go to http://www.pdml.net and follow the directions. Don't forget to visit the Pentax Users' Gallery at http://pug.komkon.org .
