Examples of theory in the following topics:
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- The kinetic theory of gases describes a gas as a large number of small particles (atoms and molecules) in constant, random motion.
- The kinetic theory of gases describes a gas as a large number of small particles (atoms or molecules), all of which are in constant, random motion.
- Kinetic theory explains macroscopic properties of gases (such as pressure, temperature, and volume) by considering their molecular composition and motion.
- In kinetic theory, the temperature of a classical ideal gas is related to its average kinetic energy per degree of freedom Ek via the equation:
- (R: ideal gas constant, n: number of moles of gas) from a microscopic theory.
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- Atomic theory is a scientific theory of the nature of matter which states that matter is composed of discrete units called atoms.
- Atomic theory is a scientific theory of the nature of matter which states that matter is composed of discrete units called atoms , as opposed to the obsolete notion that matter could be divided into any arbitrarily small quantity.
- Philosophical proposals regarding atoms have been suggested since the years of the ancient Greeks, but John Dalton was the first to propose a scientific theory of atoms.
- He based his study on two laws about chemical reactions that emerged (without referring to the notion of an atomic theory) in the late 18th century.
- For this reason, Dalton is considered the originator of modern atomic theory.
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- The terms model, theory, and law have exact meanings in relation to their usage in the study of physics.
- Some theories include models to help visualize phenomena, whereas others do not.
- A theory, in contrast, is a less concise statement of observed phenomena.
- For example, the Theory of Evolution and the Theory of Relativity cannot be expressed concisely enough to be considered a law.
- The biggest difference between a law and a theory is that a law is much more complex and dynamic, and a theory is more explanatory.
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- According to the theory of determinism, for everything that happens there are conditions such that, given those conditions, nothing else could happen.
- Albert Einstein (shown in , himself one of the founders of quantum theory) disliked this loss of determinism in measurement in the Copenhagen interpretation.
- Einstein held that there should be a local hidden variable theory underlying quantum mechanics and, consequently, that the present theory was incomplete.
- He produced a series of objections to the theory, the most famous of which has become known as the Einstein-Podolsky-Rosen (EPR) paradox.
- (According to the theory of relativity, nothing can travel faster than the speed of light in a vacuum.
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- Pressure is explained by kinetic theory as arising from the force exerted by molecules or atoms impacting on the walls of a container.
- We can gain a better understanding of pressure (and temperature as well) from the kinetic theory of gases, which assumes that atoms and molecules are in continuous random motion.
- Pressure is explained by kinetic theory as arising from the force exerted by molecules or atoms impacting on the walls of a container, as illustrated in the figure below.
- This is a first non-trivial result of the kinetic theory because it relates pressure (a macroscopic property) to the average (translational) kinetic energy per molecule which is a microscopic property.
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- (See our previous lesson on "Galilean-Newtonian Relativity. ") One issue, however, was that another well-established theory, the laws of electricity and magnetism represented by Maxwell's equations, was not "invariant" under Galilean transformation—meaning that Maxwell's equations don't maintain the same forms for different inertial frames.
- In his "Special Theory of Relativity," Einstein resolved the puzzle and broadened the scope of the invariance to extend the validity of all physical laws, including electromagnetic theory, to all inertial frames of reference.
- With two deceptively simple postulates and a careful consideration of how measurements are made, Einstein produced the theory of special relativity.
- Einstein accepted the result of the experiment and incorporated it in his theory of relativity.
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- ., of gravitational waves) predicted by current theories.
- In the theory of relativity, c interrelates space and time in the Lorentz transformation; it also appears in the famous equation of mass-energy equivalence: E = mc2.
- This invariance of the speed of light was postulated by Einstein in 1905 after being motivated by Maxwell's theory of electromagnetism and the lack of evidence for "luminiferous aether"; it has since been consistently confirmed by many experiments.
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- But, despite years of efforts by many great minds, no one had a workable theory.
- (It was a running joke that any theory of atomic and molecular spectra could be destroyed by throwing a book of data at it, so complex were the spectra.)
- Again, we see the interplay between experiment and theory in physics.
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- Planck's quantum hypothesis is a pioneering work, heralding advent of a new era of modern physics and quantum theory.
- Predictions based on classical theories failed to explain black body spectra observed experimentally, especially at shorter wavelength.
- Black line is a prediction of a classical theory for an object at 5,000K, showing catastropic discrepancy at shorter wavelengh.
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- Quantum electrodynamics (QED), a relativistic quantum field theory describing the interaction of electrically charged particles, has successfully predicted minuscule corrections in energy levels.
- This kind of spectroscopic precision allows physicists to refine quantum theories of atoms, by accounting for minuscule discrepancies between experimental results and theories.