Foundational quantum physics Foundational quantum physics In physics, atomic theory is a theory of the nature of matter. It states that all matter is composed of atoms. The philosophical background of the atomic theory is called atomism. The theory applies to the common phases of matter, namely solids, liquids and gasses, as directly experienced on Earth. Strictly speaking, it is not the appropriate theory for plasmas or neutron stars where unusual environments such as extremes of temperature or density prevent atoms from forming. ...more on Wikipedia about "Atomic theory"
Auger emission (pronounced Oh-zhay) is a phenomenon in physics in which the emission of an electron from an atom causes the emission of a second electron. This second ejected electron is called an Auger electron. ...more on Wikipedia about "Auger electron"
In atomic physics, the Bohr model depicts the atom as a small, positively charged nucleus surrounded by electrons in orbit - similar in structure to the solar system, but with electrostatic forces providing attraction, rather than gravity. Its key success was in explaining the Rydberg formula for the spectral emission lines of atomic hydrogen; while the Rydberg formula had been known experimentally, it did not gain a theoretical underpinning until the Bohr model was introduced. The Bohr model is not a complete model of the atom, and fails to explain many of the finer structures seen in atoms. As a theory, it has been replaced by quantum mechanics, and thus may be considered to be an obsolete scientific theory. However, because of its simplicity, the Bohr model is still commonly taught to introduce students to quantum mechanics. ...more on Wikipedia about "Bohr model"
In quantum mechanics, the Compton scattering or Compton effect, observed by Arthur Holly Compton in 1923 that won him the 1927 Nobel Prize in Physics, is the increase in wavelength (decrease in energy) which occurs when X-ray (or gamma ray) photons with energies of around 0.5 MeV to 3.5 MeV interact with electrons in a material. The amount the wavelength increases by is called the Compton shift. Compton's experiment became the ultimate observation that convinced all physicists that light can behave as a stream of particles whose energy is proportional to the frequency. ...more on Wikipedia about "Compton scattering"
(Davisson-Germer experiment) In 1927 at Bell Labs, Clinton Davisson and Lester Germer fired slow moving electrons at a crystalline nickel target. The angular dependence of the reflected electron intensity was measured, and was determined to have the same diffraction pattern as those predicted by Bragg for X-Rays. ...more on Wikipedia about "Davisson-Germer experiment"
In physics, the de Broglie hypothesis is the statement that all matter has a wave-like nature ( wave-particle duality) and that the wavelength and momentum of a particle are related by a simple equation. The hypothesis was advanced by Louis de Broglie in 1923 in his PhD thesis; he was awarded the Nobel Prize for Physics in 1929 for this work. ...more on Wikipedia about "De Broglie hypothesis"
The double-slit experiment consists of letting light diffract through two slits producing fringes on a screen. These fringes or interference patterns have light and dark regions corresponding to where the light waves have constructively and destructively interfered. The experiment can also be performed with a beam of electrons or atoms, showing similar interference patterns; this is taken as evidence of the " wave-particle duality" predicted by quantum physics. Note, however, that a double-slit experiment can also be performed with water waves in a ripple tank; the explanation of the observed wave phenomena does not require quantum mechanics in any way. The phenomenon is quantum mechanical only when quantum particles, such as atoms or electrons, manifest as waves. ...more on Wikipedia about "Double-slit experiment"
In physics, the Franck-Hertz experiment was an early physics experiment that provided support for the Bohr model of the atom, a precursor to quantum mechanics. In 1914, physicists James Franck and Gustav Ludwig Hertz sought to experimentally probe the energy levels of the atom. The now-famous Franck-Hertz experiment elegantly supported Niels Bohr's model of the atom, with electrons orbiting the nucleus with specific, discrete energies. Franck and Hertz were awarded the Nobel Prize in Physics in 1925 for this work. ...more on Wikipedia about "Franck-Hertz experiment"
The Gold foil experiment, or Geiger-Marsden experiment was an experiment done by Hans Geiger and Ernest Marsden in 1909, under the direction of Ernest Rutherford at the Physical Laboratories of the University of Manchester which led to the downfall of the plum pudding model of the atom. ...more on Wikipedia about "Gold foil experiment"
In atomic physics, hyperfine structure is a small perturbation in the energy levels (or spectrum) of atoms or molecules due to the magnetic dipole-dipole interaction, arising from the interaction of the nuclear magnetic dipole with the magnetic field of the electron. ...more on Wikipedia about "Hyperfine structure"
Incompleteness of quantum physics is the assertion that the state of a physical system, as formulated by quantum mechanics, does not give a complete description for the system. A complete description is one which uniquely determines the values of all its measurable properties. The existence of indeterminacy for some measurements is a characteristic of quantum mechanics; moreover, bounds for indeterminacy can be expressed in a quantitative form by the Heisenberg uncertainty principle. ...more on Wikipedia about "Incompleteness of quantum physics"
The purpose of Robert Millikan's oil-drop experiment ( 1909) was to measure the electric charge of the electron. He did this by carefully balancing the gravitational and electric forces on tiny charged droplets of oil suspended between two metal electrodes. Knowing the electric field, the charge on the droplet could be determined. Repeating the experiment for many droplets, it was found that the values measured were always multiples of the same number. This was taken to be the charge on a single electron: 1.602 × 10−19 coulombs ( SI unit for electric charge). ...more on Wikipedia about "Oil-drop experiment"
The photoelectric effect is the emission of electrons from matter upon the absorption of electromagnetic radiation, such as ultraviolet radiation or x-rays. An older term for the photoelectric effect was the Hertz effect, though this phrase has fallen out of current use. ** ...more on Wikipedia about "Photoelectric effect"
The Planck Postulate (or Planck's Postulate) was used by Max Planck in his derivation of his law of black body radiation. It is the postulate that the energy of oscillators in a black body is quantised by: ...more on Wikipedia about "Planck postulate"
In physics, the spectral intensity of electromagnetic radiation from a black body at temperature T is given by the Planck's law of black body radiation: ...more on Wikipedia about "Planck's law of black body radiation"
In physics, the Plum pudding model of the atom was made after the discovery of the electron and was proposed by the discoverer of the electron, J. J. Thomson. The model, however, preceded the discovery of the proton or neutron. In it, the atom is envisioned as electrons surrounded by a soup of positive charge, like plums surrounded by pudding. The electrons were positioned uniformly throughout the atom. Instead of a soup, the model is also said to have had a cloud of positive charge. This model was disproved by an experiment by Ernest Rutherford, the gold foil experiment, when he discovered the nucleus of the atom. ...more on Wikipedia about "Plum pudding model"
In physics, the Rayleigh-Jeans Law, first proposed in the early 20th century, expresses the energy density of blackbody radiation of wavelength λ as ...more on Wikipedia about "Rayleigh-Jeans law"
In physics, Rutherford scattering is a phenomenon that was explained by Ernest Rutherford in 1911, and led to the development of the orbital theory of the atom. It is now exploited by the materials analytical technique Rutherford backscattering. Rutherford scattering is also sometimes referred to as Coulomb scattering because it relies on static electric ( Coulomb) forces. A similar process probed the insides of nuclei in the 1960s, called deep inelastic scattering. ...more on Wikipedia about "Rutherford scattering"
The Rydberg formula (Rydberg-Ritz formula) is used in atomic physics for determining the full spectrum of light emission from hydrogen, later extended to be useful with any element. ...more on Wikipedia about "Rydberg formula"
In quantum mechanics, a state function is a linear combination (a superposition) of eigenstates (the exception is if a state function is itself an eigenstate). In the Schrödinger picture, all of these eigenstates are constantly rotating through time. ...more on Wikipedia about "Schrödinger picture"
The first Shelter Island Conference on the Foundations of Quantum Mechanics was held from June 2-4, 1947 at the Ram's Head Inn in Shelter Island, New York. The most famous participant, J. Robert Oppenheimer, deemed it the most successful scientific meeting he had ever attended. A relatively young Richard Feynman would later observe, "There have been many conferences in the world since, but I've never felt any to be as important as this." The conference cost $850. ...more on Wikipedia about "Shelter Island Conference"
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In physics, the Stark effect is the splitting and shift of a spectral line into several components in the presence of an electric field. The amount of splitting itself is called the Stark shift. It is analogous to the Zeeman effect where a spectral line is split into several components in the presence of a magnetic field. The Stark effect is responsible for the pressure broadening ( Stark broadening) of spectral lines by charged particles. ...more on Wikipedia about "Stark effect"
In quantum mechanics, the Stern-Gerlach experiment, named after Otto Stern and Walther Gerlach, is a celebrated experiment in 1920 on deflection of particles, often used to illustrate basic principles of quantum mechanics. It can be used to demonstrate that electrons and atoms have intrinsically quantum properties, that measurement in quantum mechanics affects the particles measured, and that quantum states are necessarily described by complex numbers. ...more on Wikipedia about "Stern-Gerlach experiment"
The ultraviolet catastrophe, also called the Rayleigh-Jeans catastrophe, was a prediction of early 20th century classical physics that an ideal black body at thermal equilibrium will emit radiation with infinite power. As observation showed this to be clearly false, it was one of the first clear indications of problems with classical physics. The solution to this problem led to the development of an early form of quantum mechanics. ...more on Wikipedia about "Ultraviolet catastrophe"
In physics, wave-particle duality holds that light and matter can exhibit properties of both waves and of particles. It is a central concept of quantum mechanics. The idea is rooted in a debate over the nature of light and matter dating back to the 1600s, when competing theories of light were proposed by Christiaan Huygens and Isaac Newton. Through the work of Albert Einstein, Louis de Broglie and many others, it is now established that small objects, such as atoms, have both wave and particle nature, and that quantum mechanics provides the over-arching theory resolving this apparent paradox. ...more on Wikipedia about "Wave-particle duality"
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