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In probability theory, an "expectation value" is the average of all values of a measurable quantity that one would expect, if a measurement was repeated a large number of times on a given system. For example, for an unbiased coin, the expectation value for "heads" is half of all tosses.
Each measurable quantity of a quantum system has an operator that, when mathematically applied to the system, gives a value of that quantity for that system. The expectation value for that quantity, for a given quantum system, is the product of that operator on a given state of the system, times the probability of the system being in that state, integrated over all possible states of the system. A more formally stated example:
For a quantum state Ψ(x), where 'x' can vary from -∞ to ∞, and for which Q(x) is a measurable quantity, then the expectation value of Q(x) would be equal to
∫Ψ*(x)Ψ(x)Q(x)dx
integrated from x = -∞ to x = ∞
As an example, suppose we wanted the expectation value for the radial position of an electron in its '1S' state within a hydrogen atom. When doing the formal math, we find that this value exactly equals the Bohr Radius. In contrast to the Bohr Model of an atom, this expectration value does NOT state that this electron IS at this radius, only that an AVERAGE of all radial measurements of such an electron would be the Bohr Radius.
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What is a mixed state in quantum mechanics?
The mixed state in quantum mechanics is the statistical ensemble of the pure states.
What is the alternative to quantum mechanics?
Classical Mechanics and Wave Theory.
What is the Alternative to the Quantum Mechanics theory?
There is no reasonable alternative to quantum mechanics, at least not something that can even compare with the predictive power and experimental accuracy as quantum theory. If you want to make predictions about things happening at small scales you cannot do without quantum mechanics. Also note that certain models which are now considered as possible theories of everything (e.g. string theory) all expand upon quantum mechanics, they do not make quantum mechanics invalid or unnecessary.
Quantum Mechanics for Dummies?
This is the title of a book that teaches how to perform the calculations of Quantum Mechanics, in very simple easy to follow terms.
How does light waves and radioactive decay relate to Quantum Mechanics?
Because light waves and radioactive decay are some of the key factors that lead to the development of Quantum Mechanics. Quantum mechanics is also our best apparatus for describing and predicting those phenomena.
Why expectation values are used?
In quantum mechanics,we are not certain about any physical quantity(unlike classical echanics).So,here value of every physical quantity can only be approximated or expected
When was Principles of Quantum Mechanics created?
Principles of Quantum Mechanics was created in 1930.
Why it is said relativistic quantum mechanics?
The distinction is sometimes made to distinguish normal quantum mechanics (which does not incorporate special relativity) and quantum field theory (relativistic quantum mechanics). Since we know special relativity is correct it is the relativistic form of quantum mechanics which is true, but non-relativistic quantum mechanics is still used, because it is a good approximation at low energies and it is much simpler. Physics students typically study regular quantum mechanics before moving on to quantum field theory.
Is newton known for quantum mechanics?
The concepts of quantum mechanics were not explored until the 20th century. Newton only lived into the 18th century, so Newton did no work on quantum mechanics.
What is a mixed state in quantum mechanics?
The mixed state in quantum mechanics is the statistical ensemble of the pure states.
Who created Quantum Mechanics and is it true that it is replacing the old physics?
Quantum Mechanics "replaced" Classical Mechanics in particle physics in mid-1930s.
Why quantum mechanics is someone called wave mechanics?
It is also called wave mechanics because quantum mechanics governed by Schrodinger's wave equation in it's wave-formulation.
What is the alternative to quantum mechanics?
Classical Mechanics and Wave Theory.
Is quantum mechanics a set of fields or is it just a lone branch of mechanics?
Quantum mechanics is a separate branch of physics. It is a general term given to all quantum physics. There are many subbranches, for example Quantum chronodynamics which describes the strong nuclear interaction.
What is the Alternative to the Quantum Mechanics theory?
There is no reasonable alternative to quantum mechanics, at least not something that can even compare with the predictive power and experimental accuracy as quantum theory. If you want to make predictions about things happening at small scales you cannot do without quantum mechanics. Also note that certain models which are now considered as possible theories of everything (e.g. string theory) all expand upon quantum mechanics, they do not make quantum mechanics invalid or unnecessary.
Why plasma is not explained with quantum mechanics?
I am not aware of it "not being explained". I would guess that you can explain the relevant aspects with quantum mechanics.
What was The idea that light can act as packets led to what new field of science?
Quantum mechanics
