Adding a "sharp eye" to the problem does change the result =>
no interference pattern is seen as long as the viewer stays focused!
The "eye" is equivalent to using a lens and the same viewing screen. The most simple and definitive way for me to think about it is based in fundamental optics, so I will describe the possible outcomes with a lens and the existing viewing screen.
1. IF the lens is positioned to exactly
image the slits on the screen (the sharp eye resolving the slits), then by optical theory, the intensity distribution of object plane is duplicated (with magnification) at the image plane (the viewing screen). Since there is no interference at the plane of the slits,
there will be no interference at the image plane. What you will see is the image of the two slits, back-lit. (Beta, you may be the closest)
2. IF the lens is positioned so the viewing screen is at its focus (ol' Sharp Eye is fatigued and relaxes to focus at infinity), the interference pattern will then be visible. First of all, normal creation and analysis of interference is typically done at the focal plane a lens. Why? The lens focus, or transform plane, "images" the far-field of the incident light on the lens - at the lens focal plane, the "image"
is the intensity distribution at infintiy. Pure interference is ideally characterized in "angle space", or far field, which is explicitly, and ALWAYS obtained at the lens focal plane. I.e. at the lens focal plane, the intensity distribution is identical to the intensity distribution at infinity (in angle space)
without the lens. Therefore, in a dark room, the relaxed eye will see (if not already blinded by a laser
) an interference pattern.
3. IF the lens is position somewhere in between ('ol Sharp Eye is struggling to regain focus of the slits),
I speculate that there will be a mix of interference and image information. So maybe like Chris's explanation, the slightly blurred, partially resolved slits will show some intensity modulation (ol' Sharp Eye moves his head side to side and sees intensity changes overlaid on the slit images).
Let me just say, my profession is working / building / designing laser resonators, simple imaging systems and interferometers. Although I haven't done this experiment, I am using acquired knowledge and experience, and these descriptions are based on fundamental properties of lenses and imaging.
Adding a "sharp eye" to the problem does change the result => [size=150][b]no interference pattern is seen as long as the viewer stays focused![/b][/size]
The "eye" is equivalent to using a lens and the same viewing screen. The most simple and definitive way for me to think about it is based in fundamental optics, so I will describe the possible outcomes with a lens and the existing viewing screen.
1. IF the lens is positioned to exactly [u]image[/u] the slits on the screen (the sharp eye resolving the slits), then by optical theory, the intensity distribution of object plane is duplicated (with magnification) at the image plane (the viewing screen). Since there is no interference at the plane of the slits, [u]there will be no interference at the image plane[/u]. What you will see is the image of the two slits, back-lit. (Beta, you may be the closest)
2. IF the lens is positioned so the viewing screen is at its focus (ol' Sharp Eye is fatigued and relaxes to focus at infinity), the interference pattern will then be visible. First of all, normal creation and analysis of interference is typically done at the focal plane a lens. Why? The lens focus, or transform plane, "images" the far-field of the incident light on the lens - at the lens focal plane, the "image" [u]is[/u] the intensity distribution at infintiy. Pure interference is ideally characterized in "angle space", or far field, which is explicitly, and ALWAYS obtained at the lens focal plane. I.e. at the lens focal plane, the intensity distribution is identical to the intensity distribution at infinity (in angle space) [u]without[/u] the lens. Therefore, in a dark room, the relaxed eye will see (if not already blinded by a laser :shock:) an interference pattern.
3. IF the lens is position somewhere in between ('ol Sharp Eye is struggling to regain focus of the slits), [i]I speculate[/i] that there will be a mix of interference and image information. So maybe like Chris's explanation, the slightly blurred, partially resolved slits will show some intensity modulation (ol' Sharp Eye moves his head side to side and sees intensity changes overlaid on the slit images).
Let me just say, my profession is working / building / designing laser resonators, simple imaging systems and interferometers. Although I haven't done this experiment, I am using acquired knowledge and experience, and these descriptions are based on fundamental properties of lenses and imaging.