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<<College Physics>> Edition 2 Paul Peter Urone P731
Measurement disturbs the system being observed. Information can be lost, and in some cases it is imposible to measure two physical quantities simultaneously to exact precision...Those probes have momentum themselves,and by scattering from the eletron,they change its momentum in a manner that loses information...their is a limit to absolute knowledge, even in principle.
<<Physics for Scientists and Engineers with Modern Physics>> 3nd Ed D.C.Giancoli P795
But according to quantum mechanics, there is actually a limit to the accuracy of certain measurements. This limit is not a restriction on how well instruments can be made, it is inherent in nature. It is the result of two factors: the wave-particle duality, and the unavoidable interaction between the thing observed and the observing instrument. Let us look at this in more detail…
http://abyss.uoregon.edu/~js/21s ... lectures/lec14.html
Any attempt to measure precisely the velocity of a subatomic particle, such as an electron, will knock it about in an unpredictable way, so that a simultaneous measurement of its position has no validity. This result has nothing to do with inadequacies in the measuring instruments, the technique, or the observer; it arises out of the intimate connection in nature between particles and waves in the realm of subatomic dimensions.
http://www.answers.com/topic/uncertainty-principle
The principle that it is not possible to know with unlimited accuracy both the position and momentum of a particle. This principle, discovered in 1927 by Werner Heisenberg, is usually stated in the form: ΔxΔpx ≥ h/4π, where Δx is the uncertainty in the x-coordinate of the particle, Δpx is the uncertainty in the x-component of the particle's momentum, and h is the Planck constant.
An explanation of the uncertainty is that in order to locate a particle exactly, an observer must be able to bounce off it a photon of radiation; this act of location itself alters the position of the particle in an unpredictable way. To locate the position accurately, photons of short wavelength would have to be used. These would have associated large momenta and cause a large effect on the position. |
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