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  • o

  • open sytemSee system. Read More
  • operatorIn mathematics, “operator” has two main definitions. 1) An operator is a mathematical symbol, for example +, that represents(...) Read More
  • orbitalIn the early 1900's, when physicists were first probing the insides of the atom, they thought that electrons might travel(...) Read More
  • orbital angular momentum(Symbol: ɭ or L). Electrons have two types of rotational motion: orbital angular momentum and spin. Orbital angular momentum(...) Read More
  • ordinary matterScientists call the everyday matter of our world, such as tables and chairs, “ordinary matter.” Ordinary matter is made up(...) Read More
  • oscillationDefinition (1): An oscillation is a repetitive back-and-forth motion. A pendulum swinging back and forth is an everyday(...) Read More
  • oscillatorAn oscillator is something that oscillates. Something that vibrates. See oscillation for more information. [caption(...) Read More
  • p

  • particleIn everyday speech, a particle is a bit of matter. I might say that there is particle of dirt on the lens of my glasses.(...) Read More
  • particle-wave dualityWhen a photon hits your eye, it’s a particle. When it hits your eye, it interacts with a particular electron in the retina(...) Read More
  • periodIf you were standing on a dock and water waves were coming at you, the period would be the time interval between waves. In(...) Read More
  • Periodic Table of the ElementsThe Periodic Table of the Elements lists all the elements, over 100 of them, in a specific sequence. This includes the(...) Read More
  • physical constantThe constant c, the speed of light in a vacuum, is an example of a physical constant. It is a constant of nature, always(...) Read More
  • piPi is symbolized π and pronounced like "pie." It is the mathematical symbol for the number 3.14159…, which goes on(...) Read More
  • Pilot Wave Interpretation of quantum mechanicsThis interpretation of quantum mechanics is also called the "Bohmian Interpretation." It was originally proposed by(...) Read More
  • probability amplitude“Probability amplitude” is a term used in quantum physics. It’s a number that appears in Schrodinger’s Wave Equation. Let’s(...) Read More
  • probability waveMax Born, one of the early quantum physicists in the 1920's and '30s, proposed that between detections, quantum particles(...) Read More
  • q

  • QFTSee Quantum Field Theory. Read More
  • quantities of dimension oneFor “quantities of dimension one,” see “dimensionless number.” Read More
  • quantumOne definition of “quantum” is: a tiny packet of energy at the atomic level. A quantum is the smallest possible unit of(...) Read More
  • quantum angular momentumFor quantum angular momentum, see angular momentum. Read More
  • quantum decoherenceFor quantum decoherence, see  decoherence. Read More
  • quantum entanglementIn quantum physics, if two particles are entangled, their behavior is correlated. In addition, if a physicist obtains(...) Read More
  • Quantum Field TheoryQuantum Field Theory (QFT) is the current theory of how atomic and subatomic particles behave. It is the most up-to-date(...) Read More
  • quantum mechanicsIn quantum mechanics, physicists study how tiny particles behave. These include atoms, the components of atoms like(...) Read More
  • quantum numberElectrons have a few handfuls of properties. Four have been selected as the electron’s “quantum numbers.” The quantum(...) Read More
  • quantum physicsFor an understanding of quantum physics, see the definition of "quantum mechanics." Often, the two terms are used to mean(...) Read More
  • quantum randomnessMany quantum physicists view quantum mechanics as differing from classical physics in a fundamental way—quantum mechanics is(...) Read More
  • quantum realmA number of interpretations of quantum mechanics postulate a “quantum realm.” These include the Transactional(...) Read More
  • quantum spinSee "spin." Read More
  • quantum theory“Quantum theory” is the original name for the field that became known as “quantum mechanics" (which see). The connotations(...) Read More