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View Full Version : Can Interferance cause magnification?


pallidin
Jul11-04, 04:58 PM
There is this house down the street which has one of those new, white plastic vinyl fences around the front yard.
This particular fence is constructed in such a way as the vertical members are the width of the spacing between members(about 2 inches or so)
More importantly, the top of the fence line changes horozontaly, kind of like a wave(I suppose for aesthetic reasons) with some ornamental du-dad fashioned atop each vertical fence element.

Anyway, when I drive to work each morning, the sun is above and behind the fence.
I notice the interferance pattern, but a startling thing happens as I approach, roughly, about 100 feet from it:
A black and white interferance image of the back fence, with all the du-dads, appears with exceptional crispness and is about 4-times larger(width-wise) than the fence itself.
It is an awesome sight, an have seen it hundreds of times. It appears as though I am looking at a magnified negative image of the back fence with exquisite detail. When the sun is not behind it the image is barely noticable.
Is this a common feature of interferance patterns?
Also, if I take the time to take pictures, will the phenomenon show up?

pallidin
Jul11-04, 05:08 PM
I should point-out that the exceptionally fine detail I see is with respect to the outline of the back fence and top du-dads. No "non-edge" detail is observable.

chroot
Jul11-04, 07:37 PM
Well, if your eye can see it, so can a camera...

- Warren

maverick280857
Jul13-04, 12:56 AM
Do you mean magnification of the fringes (by your first topic)?

sporff
Jul14-04, 09:25 PM
Where does the pattern appear? That's the only thing i can't follow. Sounds interesting though. Can you snap a few pictures?

NSX
Jul14-04, 09:32 PM
I'm thinking what sporff is too [unless I misunderstood your message].

In my Serway (http://www.brookscole.com/cgi-brookscole/course_products_bc.pl?fid=M2&discipline_number=13&product_isbn_issn=003026961X), it says that interference patterns only occur when the spacing between the slits is approximately that of the wavelength of the EMR.

pallidin
Jul15-04, 08:17 PM
Thanks all, I've been away. I will more closely examine this to correct or further address the issue.
I am not sure that this is not some type of optical illusion or mis-interpretation on my part. Nonetheless I will endeavor to more accurately experience the event(it has previously always been by a moving car), so I will do a "walk-by" in the next week.