Re: Double slit experiment explained.

From: Sam Wormley (swormley1_at_mchsi.com)
Date: 11/20/04 

Date: Sat, 20 Nov 2004 01:19:00 GMT

Young's Double Slit Experiment
   http://scienceworld.wolfram.com/physics/YoungsDoubleSlitExperiment.html
   http://scienceworld.wolfram.com/physics/DoubleSlitInterference.html

Fraunhofer Diffraction--Double Slit
   http://scienceworld.wolfram.com/physics/FraunhoferDiffractionDoubleSlit.html

PHYSICS NEWS UPDATE
   http://www.aip.org/enews/physnews/2002/split/613-1.htm
The American Institute of Physics Bulletin of Physics News
Number 613 November 13, 2002 by Phillip F. Schewe, Ben Stein, and James
Riordon

A BI-PHOTON DE BROGLIE WAVELENGTH has been directly measured in an
interference experiment for the first time. In the early days of quantum
mechanics, Louis de Broglie argued that if waves could act like particles
(photoelectric effect) then why couldn't particles act like waves? They
could, as was borne out in numerous experiments (the double-slit experiment
for electrons was voted the "most beautiful" experiment in a recent poll-see
Physics World, Sept 2002). In fact intact atoms in motion and even
molecules can be thought of as "de Broglie waves." Molecules as large as
buckyballs (carbon-60) have been sent through an interferometer, creating a
characteristic interference pattern (see Update 579,
http://www.aip.org/enews/physnews/2002/split/579-1.html). The measured
wavelength for a composite object like C-60 will in part depend on the
internal bonds of the molecule. What then if the corporate object is a
pair of entangled photons?

One of the more fascinating predictions made regarding quantum entanglement
(Jacobson et al., Physical Review Letters, 12 Jun 1995) was the suggestion
that the de Broglie wavelength for an ensemble consisting of N entangled
photons (each with a wavelength of L) would be L/N. This proposition has
been verified now by physicists at Osaka University (Keiichi Edamatsu,
81-6-6850-6507, eda@mp.es.osaka-u.ac.jp) for the case of two entangled
photons. The daughter photons were created by the process of parametric
down-conversion, in which an incident photon entering a special crystal will
split into two correlated photons. These photons are then sent through an
interferometer (see figure at http://www.aip.org/mgr/png/2002/169.htm). The
resultant interference pattern shows that the photons behave as if they
acted as a single entity with a wavelength half that for either photon
alone, a feature which might improve the sharpness of future quantum
lithography (the narrowness of lines on a circuit board being no better than
the wavelength of light used in the fabrication process). But since the
parent photon already had this shorter wavelength, what will have been
gained by splitting the photon in half? The advantage will come when, at
some point in the future it will be possible to generate entangled photons
from non-entangled photons of the same wavelength, a process called
hyper-parametric scattering. (Edamatsu et al., Physical Review Letters, 18
November 2002)

Also: http://www.google.com/search?q=%22double-slit%22+site%3Awww.aip.org+update

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