Heisenberg also introduced the Uncertainty Principle and this may be written down in two equations: -
Îx. Îp â ħ
And
ÎE. Ît â ħ
The first equation states that the product of the momentum spread (for a quantum entity) and special spread is approximately equal to Planck’s constant divided by 2 pi. In the second equation, the spread of energy and spread of time products are approximately equated to Planck’s constant divided by 2 pi.
In effect the first equations says that, the greater the precision with which we know the value of the position (x), of a quantum entity, then the greater the spread or uncertainty of its momentum and vice a versa. Similarly, from the second equation, the greater the spread in energy, of the quantum particle of entity, then the shorter the time it can exist and again, vice a versa.
A quick partial proof of the first equation may be made as follows. Consider an electron to be a wave packet of allowed wave vectors
k= (2 Ï/L)(lx,ly,lz)
And an allowed spectrum of frequencies: -
Ï = ck = (2 Ï.c/L) â (lx,ly,lz)
It may be shown (the actual derivation requires several applications of calculus methods, which are difficult to type down in this answer format) that the special (x) spread of a wave packet as a product of its wave vector spread has the criteria: -
Îx. Îk ⥠1
Since Îp = ħ Îk a substitution for Îk in terms of Îp gives : -
Îx. Îp â ħ
The second equation may be derived from a consideration and time and frequency spreads (E = hf).
2007-12-28 06:25:25
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answer #2
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answered by . 6
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for principle
http://en.wikibooks.org/wiki/Quantum_Mechanics/Heisenberg_Uncertainty_Principle
derivation and expalnation
http://en.wikipedia.org/wiki/Uncertainty_principle
2007-12-28 05:32:07
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answer #4
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answered by ::Ð嬢Y¢LøÞs:: 3
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I was going to, but.............I'm not there anymore.
2007-12-28 07:07:59
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answer #5
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answered by craig b 7
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