Tag Info

New answers tagged

6

Quantum mechanical postulates So is the mathematical expression for each individual operator also a postulate that's not listed, or are they derivable from other axioms? The mathematical expression for each individual operator is sort of a postulate, but it should not be listed. The postulates define a (more or less) complete theory in that I can ...


0

I believe that the important thing to remember is the basic difference between quantum and classical description of a system. In classical mechanics you describe it by defining some sort of equation of motion which gives you a position of all the constituents of the system described by function of time but for each of these particles you have one function. ...


2

Third law: analysis We have seen that in '63 Huygens exposed his theory to the Royal Society and in '68 he submitted his paper to the PT of RS in which he presented his law of momentum: "Quantitas motum duorum Corporum augeri minuive potest per eorum occursum; at semper ibi remanet eadem quantitas versus eandem partem, ablata inde quantitate motus ...


2

In 1988, Weinberg used an equivalent relation as an historical starting point for the weak anthropic principle, in his "The cosmological constant problem". I quote, page 7: An example is provided by what I think is the first use of anthropic arguments in modern physics, by Dicke (1961), in response to a problem posed by Dirac (1937). In effect, Dirac ...


1

The photoelectric effect issue was motivated by the evidence that increasing the amount of radiation of a given wavelength doesn't make an electron jump out from the atom. Only increasing the frequency of the radiation above a given threshold ionized the atom. So, Einstein decided that e.m. radiations is corpuscular, quantized, and each quantum carries an ...


9

This is the plum pudding model of the atom Left: Expected results: alpha particles passing through the plum pudding model of the atom undisturbed. Right: Observed results: a small portion of the particles were deflected, indicating a small, concentrated positive charge. There are no electrons and no outer shells, quantum mechanics was yet to come ...


8

The $\alpha$ particle, attracted by the electrons on the outer shell of the pudding, orbits nearly parabolically around the atom, causing the near-180 degree deflection angle seen. This wouldn't happen because of momentum conservation. It was reasonably established in 1909 (when the gold foil experiment was done) that electrons were light, so if an ...


0

Based on thomson's model, all of the alpha particles should go through or reflect back but in Rutherford's experiment, it was more of in between, some reflecting back and some going through, disproving the theory.


1

Maxwell's thermodynamics and E&M were both atomistic. For example, in his Treatise on Electricity and Magnetism §255, he found it extremely natural to suppose that the currents of the ions are convection currents of electricity, and, in particular, that every molecule of the cation is charged with a certain fixed quantity of positive electricity, ...


2

Boltzmann's version of entropy require a finite number of states, and Planck had asserted that probability has no meaning without a “finite number of equally likely configurations.”{1} That is, in order to be able to use Boltzmann's equation and obtain finite results, he needed to use a discrete number of states, but light was supposed to be continuous. ...



Top 50 recent answers are included