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All of quantum mechanics is contained in the two-slit experiment; 
unfortunately, no one understands the two-slit experiment – Feynman
Text Box: Richard Feynman's elaboration of the two-slit experiment* is a classic discussion of wave-particle duality and the uncertainty principle. ...
*Feynman, R. P., Leighton, R. B. & Sands, M. L. The Feynman Lectures on Physics Vol. 3, 1-4 (Addison-Wesley, Reading, 1965)
Illuminating Entanglement, Tony Sudbery (Department of Mathematics, University of York, UK), Nature 379, 403-404
(1 February 1996)
Text Box: Frequency mixing. In three-wave sum- and difference-frequency mixing, two incident waves at n1 and n2 are converted to a third wave at n3 according to [n3 = n1 ± n2]. The simplest interaction of this type is second-harmonic generation in which n3 = 2n1. ... By using radiation from pulsed lasers, conversion efficiencies of over 90% have been achieved in second-harmonic generation. With continuous-wave lasers, it is more efficient if the nonlinear crystal is placed in the laser cavity. Conversion efficiencies of over 30% of the internal laser power have been obtained in this way for continuous-wave lasers.
Second-harmonic generation and second-order frequency mixing have been demonstrated at wavelengths ranging from the infrared to the ultraviolet, generally coinciding with the transparency range of the nonlinear crystals.
McGraw-Hill Encyclopedia of Physics, Second Edition (1993); pp 851-852
The radiaton (note spelling!) is the per-cycle quantum of the photon. It is common to all photons. Moreover, it is the one and only fundamental particle of analysis that is required for all of physics. (It is given due recognition starting with the name here.)
Radiatons thus uniquely constitute all that is nature, matter and electromagnetc radiation alike. 
(See www.sittampalam.net/Summary.pdf  for a quick, one-page overview of this ultimate concept on the nature of things.)

 The radiaton is also thus the classic perfectly elastic particle: 
mass and energy are non-transferably and intrinsically conserved (as mass-energy) in the radiaton;
 and momentum and momentum alone is transferred in any and all interactions between radiatons. 

Hence,  even the single radiaton from a photon of emission vibrationally sets off a series of wavefronts (or wavelets) 
through the vacuum field radiatons to transfer its momentum.
And it is only such (ever-expanding) wavefronts that enter the slits here, in reality.
           Go to Part 2 of 3
A Synopsis The Cosmos The Spin
ADDENDA The Cosmological Redshift The Neutrino
Two-Slit Tests The Galaxy Nuclear Reactions
NASA Tests Gravity The Sun
KamLAND Test Anti-Gravity The Pulsar
UCLA Test Relativity Superconductivity
Q and A Mass-Energy Fusion Energy
 Eugene Sittampalam
 1 September 2008