| Absolute zero | The lowest possible temperature at which a gas would have a zero volume. |
| Absorption spectrum | The spectrum of electromagnetic radiation absorbed by matter when radiation of all frequencies is passed through it. |
| Activity | The number of decays per second of a radioactive substance. |
| Antinode | The point of maximum displacement of a stationary wave. |
| Binding energy | The negative of the amount of energy needed to separate a nucleus into individual nucleons. |
| Boson | The carrier particle that mediates the weak nuclear force. |
| Capacitance | The ratio of charge stored per increase in potential difference. |
| Capacitor | An electrical device used to store charge and energy in the electrical field. |
| Circular motion | Motion with constant radius of curvature caused by a centripetal force and acceleration that is perpendicular to velocity. |
| Coherent waves | Waves that have a constant phase difference. |
| De Broglie wavelength | Length of de Broglie wave of a particle, equal to Planck’s constant divided by the momentum of the particle. |
| Elastic collision | Interaction between two objects in which kinetic energy is conserved. |
| Electric field strength | The ratio of force exerted by an electric field on a test charge to the magnitude of the charge. |
| Emission spectrum | The spectrum produced by radiation from excited atoms. |
| Energy levels | The discrete amounts of energy that an electron in an atom may have. |
| Entropy | A measure of disorder in a system. |
| Excited state | An energy level in an atom that is higher than the ground state. |
| Farad | The unit of capacitance. One farad equals one coulomb per volt. |
| First law of thermodynamics | The change in internal energy is equal to heat added and work done on system. |
| Fundamental particles | The smallest particles (quarks and leptons) of which all materials are composed. |
| Gluon | The carrier particle of the strong nuclear force. |
| Graviton | The particle that carries the gravitational force. Not yet observed. |
| Heat engine | A device that converts thermal energy to mechanical energy. |
| Heisenberg uncertainty principle | The more accurately the position of a particle is measured, the less accurately the momentum can be known, and vice versa. |
| Impulse | The product of force and time interval over which it acts. Equals the change in momentum of an object. |
| Inelastic collision | Collision in which kinetic energy is not conserved. |
| Laser | A device that produces coherent light by stimulated emission of radiation. |
| Law of universal gravitation | The gravitational force between two objects depends directly on the product of their masses and inversely on the square of their separation. |
| Lenz’s law | The magnetic field generated by an induced current opposes the change in field that caused the current. |
| Lepton | A “light” particle that does not interact with the strong nuclear force. Includes the electron and the neutrino. |
| Linear accelerator | A device that accelerates subatomic particles by applying successive electric field. |
| Neutrino | Chargeless, massless, subatomic particle emitted in beta decay. A type of lepton. |
| Photoelectric effect | The ejection of electrons from surface of metal exposed to electromagnetic radiation. |
| Photon | A quantum of electromagnetic waves and a mediator of the electromagnetic interaction.. |
| Photovoltaic cell | A device that converts electromagnetic radiation into electrical energy. |
| Planck’s constant | The ratio of energy of photon to its frequency. A fundamental constant. |
| Principle of superposition | When two waves interact, the resulting amplitude is equal to the sum of the individual amplitudes of the two waves. |
| Quark | The basic building blocks of protons, neutrons, other baryons, and mesons. |
| Resistivity | A measure of how strongly a material opposes the flow of electric current. |
| Second law of thermodynamics | Heat always flows from a region of high temperature to a region of lower temperature. |
| Simple harmonic motion | Motion caused by linear restoring force that is proportional to the square of the displacement, and that has a period independent of the amplitude of motion. |
| Superconductor | An electrical conductor that has no resistance and low temperatures. |
| Strangeness | A property of strange quarks. Strangeness is always conserved in strong interactions. |
| Strong nuclear force | Force of very short range that holds neutrons and protons in nucleus together. Mediated by gluons. |
| Synchrotron | A device to accelerate particles in which particles move in circular path. Uses magnetic fields. |
| Transistor | A semiconductor device that controls large current by means of small voltage changes. |
| Wave-particle duality | The principle that matter can exhibit both particle and wave-like properties. |
| Weak nuclear force | The force involved in beta decay of the neutron and atomic nuclei. |
| Work function | Energy needed to remove an electron from metal. Mediated by bosons. |
| Young’s modulus | A constant of proportionality associated with the change in length of a material according to its elastic properties. |
