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Branch of physics concerned with the microworld based on wave functions and probabilities, introduced by Max Planck (1900) and developed by Werner Heisenberg (1925), Erwin Schrodinger (1926), and others.
Schrodinger's wave equation
Fundamental wave equation of quantum mechanics, which interprets the wave nature of material particles in terms of probability wave amplitudes. It is as basic to quantum mechanics as Newton's law of motion are to classical mechanics.
If a new theory is valid, it must account for the verified results of the old theory in the region where both theories apply.
Ritz combination principle
For an element, the frequencies of some spectral lines are either the sum or difference of the frequencies' two other lines in that element's spectrum.
the process of forming ions(molecules of a substance broken apart)
Stream of beta particles (electrons or positrons) emitted by certain radioactive nuclei.
A device used to measure radioactive decay.
Stream of alpha particles (helium nuclei) ejected by certain radioactive nuclei.
Principal building block of the nucleus; a neutron or a proton; the collective name for either or both.
Use of radiation as a treatment to kill cancer cells.
Elementary particle in the class of elementary particles called leptons. It is uncharged and almost massless; three kinds-electron, moun, and tau neutrinos, are the most common high-speed particles in the universe; more than a bil…
Unit used to measure a dose of radiation; the amount of energy (in centijoules) absorbed from ionizing ration per kilogram of exposed material.
Force that attracts nucleons to each other within the nucleus; a force that is very strong at close distances but decreases rapidly as the distance increases. Also called strong interaction.
A device used to measure radiation from radioactive sources.
A device used to detect the paths of particles emitted by radioactive sources.
High-frequency electromagnetic radiation emitted by atomic nuclei.
(a) Abbreviation for gram. (b) When a lowercase italic g, the symbol for the acceleration due to gravity (at Earth's surface, 9…
Term applied to an atom having an unstable nucleus that can spontaneously emit a particle and become the nucleus of another element.
Acronym of roentgen equivalent man; it is a unit used to measure the effect of ionizing radiation on human beings.
Process of determining the time that has elapsed since death by measuring the radioactivity of the remaining carbon-14 isotopes.
Electromagnetic radiation, higher in frequency than ultraviolet, emitted by atoms when the innermost orbital electrons undergo excitation.
One of the two classes of elementary particles (the other is the lepton). Two of the six quarks (up and down) and the fundamental building blocks of nucleons (protons and neutrons.)
the making and breaking of chemical bonds
electron volt (eV)
Amount of energy equal to that an electron acquires in accelerating through a potential difference of 1 V.
Abbreviation for million electron volts, a unit of energy, or equivalently, a unit of mass.
Nuclear fission reactor that not only produces power but produces more nuclear fuel than it consumes by converting a non-fissionable uranium isotope into a fissionable plutonium isotope.
Nuclear fusion brought about by extremely high temperatures; in other words, the welding together of atomic nuclei by high temperature.
Minimum mass of fissionable material in a nuclear reactor or nuclear bomb that will sustain a chain reaction. A subcritical mass is one in which the chain reaction dies out. A supercritical mass is…
Self-sustaining reaction that, once started, steadily provides the energy and matter necessary to continue the reaction.
A piece of technology used to analyse types of atoms by firing them through a magnetic field in an opposite direction to an electric field. The specific charge of the ion may be found …
Splitting of an atomic nucleus, particularly that of a heavy element such as uranium-235, into two lighter elements, accompanied by the release of much energy.
Abbreviation for electron volt.
Combining of nuclei of light atoms, such as hydrogen, into heavier nuclei, accompanied by the release of much energy.
Nucleus of a deuterium atom; it has one proton and one neutron.
E = ∆mc^2
Apparatus in which controlled nuclear fission or nuclear fusion reactions take place.
Star that has undergone a gravitational collapse in which electrons are compressed into protons to form neutrons.
gravitational red shift
Shift in wavelength toward the red end of the spectrum experienced by light leaving the surface of a massive object, as predicted by the general theory of relativity.
Shortest path between points of any surface.
Study of the origin and development of the entire universe.
For sunlight and other white light, the spread of colors seen when the light is passed through a prism or diffraction grating. The colors of the spectrum, in order from lowest frequency (longest wavelength…
principle of equivalence
Observations made in an accelerating frame of reference are indistinguishable from observations made in a gravitational field.
Primordial explosion that is thought to have resulted in the creation of our expanding universe.
Gravitational disturbance that propagates through space-time made by a moving mass (undetected at this writing).
general theory of relativity
Einstein's generalization of special relativity, which deals with accelerated motion and features a geometric theory of gravitation.
L=L_0/γ, contraction is parallel to direction of motion
Occurring at the same time. In special relativity, two events that are simultaneous in one frame of reference need not be simultaneous in a frame moving relative to the first frame.
The "energy of being," given by the equation E-mc^2.
Four-dimensional continuum in which all events take place and all things exist: Three dimensions are coordinates of space and the fourth is of time.
Postulates of special relativity
(1)the speed of light in a vacuum is the same for all inertial observers. (2) the laws of physics are the same for all inertial observers.
Hypothetical particle that can travel faster than light and thus move backward in time.
special theory of relativity
Comprehensive theory of space and time that replaces Newtonian mechanics when velocities are very large; introduced in 1905 by Albert Einstein.
Study of moving electric charge, as opposed to electrostatics.
Device that uses the interference of light waves to measure very small distances with high accuracy. Michelson and Morley used an interferometer in their famous experiments with light.
frame of reference
assists one in physics in which one chooses a place (point) a measure it against changes in position.
Pertaining to the theory of relativity; or approaching the speed of light.
The distance light travels in a vacuum in one year: 9.46x10^12 km.
Moving clocks run slow