Quantum Physics Terms Already Graded A+
Photon ✔️A discrete unit or package of light energy
Photoelectric Effect ✔️The emission of electrons from a metal when electromagnetic radiation of high
enough frequency falls on the surface
Threshold Frequency (f₀) ✔️The minimum frequency of light needed to eject electrons from a metal
surface
Work Function (Φ) ✔️The minimum energy needed to eject electrons from the surface of a metal
Millikan's Stopping Potential Experiment ✔️An experiment utilizing reverse voltage raised to such a
level (stopping potential Vs) that it stops all emitted photoelectrons (NOTE: This experiment is used to
test the Einstein model of the explaining the photoelectric effect.)
de Broglie Hypothesis ✔️All particles can behave like waves whose wavelength is given by λ = h/p
where h is Planck's constant and p is the momentum of the particle.
Matter Waves ✔️All moving particles have a "matter wave" associated with them whose wavelength is
the de Broglie wavelength.
Wave-Particle Duality ✔️Both matter and radiation have a dual nature. They exhibit both particle and
wave properties.
Davisson-Germer Experiment ✔️An experiment showing that electrons are scattered off crystals of
nickel and interfere with each other - also know as "electron diffraction" (NOTE: This experiment is
evidence for the existence of matter waves.)
Electron in a Box Model ✔️A model of the atom useful for explaining the origin of atomic energy levels:
The model assumes that, if an electron is confined to move in one dimension by a box, the de Broglie
,waves associated with the electron will be standing waves of wavelength 2L/n where L is the length of
the box and n is a positive integer. Further, the kinetic energy of the electron in the box is (n²h²)/(8meL²)
Schrödinger Model of the Atom ✔️This model assumes that electrons in the atom may be described by
wavefunctions. The electron has an undefined position, but the square of the amplitude of the
wavefunction gives the probability of finding the electron at a particular point.
Heisenberg Uncertainty Principle ✔️Conjugate quantities (position-momentum or time-energy) cannot
be known precisely at the same time. (NOTE: There is a link between the uncertainty principle and the
de Broglie hypothesis. For example, if a particle has a uniquely defined de Broglie wavelength, then its
momentum is known precisely but all knowledge of its position is lost.)
alpha rays ✔️Rays that are emitted when certain radioactive atoms decay, and typically have an energy
of about 5 MeV. Are also known as alpha particles, consist of two protons and two neutrons (ppnn)
bound together into a particle identical to the nucleus of a helium atom (Z=2).
antimatter ✔️Type of matter predicted by Paul Dirac when he attempted to write down a version of
quantum mechanics that incorporated Einstein's theory of special relativity. In the Standard Model,
every particle has a corresponding antiparticle that has the same mass but opposite electric charge,
baryon number, and strangeness. When a particle meets its antiparticle counterpart, the pair
annihilates: they disappear, and their total energy is converted into other particles.
atomic number ✔️Denoted by Z, is the number of protons in its nucleus. Determines an atom's place in
the periodic table, and thus which chemical element it is.
baryon ✔️Any particle in the Standard Model that is made of three quarks. Protons and neutrons are
the most familiar particles of this type.
beta rays ✔️Rays also known as beta particles, are the electrons emitted when a neutron in the
nucleus of a radioactive atom decays into a proton. They typically have an energy of up to 2.5
MeV, sharing the total energy released in the radioactive decay with a neutrino that is produced at the
same time.
,Bevatron ✔️A particle accelerator operated at the Lawrence Berkeley National Laboratory from 1954
to 1993. It was designed to test the hypothesis that every particle has a corresponding antiparticle, and
accelerated protons to high enough energies (6.2 GeV) that antiprotons might be produced in a collision
with a fixed target. It successfully produced antiprotons, and remained a productive research facility
through several upgrades until its decommissioning in 1993.
B factory ✔️A particle physics apparatus designed to create B mesons, which are mesons that contain
one bottom antiquark and one quark of a different flavor. In this "factory", electrons and positrons from
an accelerator collide, producing B mesons and anti-B mesons in equal amounts. The science goal of this
apparatus is to study CP violation in B meson decay, which may shed light on why the universe contains
more matter than antimatter.
charge conjugation ✔️An operation that changes a particle into its antiparticle.
cloud chamber ✔️One of the earliest types of detectors used to study particles in cosmic rays and
those produced in particle accelerator collisions. Is an airtight box filled with supersaturated water
vapor. When a charged particle passes through this chamber, liquid water droplets condense out of the
vapor along the particle's path, leaving a visible trail.
CP violation ✔️A violation that occurs when an interaction
proceeds differently when the CP operation is performed—particles with opposite charge and parity
interact differently than the original particles. The CP operation is a combination of charge conjugation
(C) and parity (P). In most
interactions, CP is conserved, which means that the interaction proceeds exactly the same way if the
CP operation is performed on the interacting particles. If CP is conserved, particles with opposite charge
and parity will interact in the same way as the original particles.
cyclotron ✔️A type of particle accelerator, first developed in the 1930s, consisting of two D-shaped
cavities in a constant magnetic field. There is a gap between the cavities, so they form a circle
with a missing stripe in the middle. A radioactive source placed in the center of the accelerator —in the
gap between the cavities—provides particles that will be accelerated. When a charged particle is
emitted by the radioactive source, it is accelerated by a voltage placed across the gap. The magnetic
field bends the particle's path so it travels in a circle. When the particle circles back to the gap, it is
traveling in the opposite direction. At that point, the voltage across the gap is reversed so the particle is
accelerated further. The voltage is alternated so that the particle is accelerated each time it crosses the
gap. As the particle speeds up, its path is bent less by the magnetic field and it travels in an increasingly
, larger circle. Eventually, it spirals out of the accelerator moving at a high speed. The largest one
currently in use is TRIUMF at the University of British Columbia in Vancouver, Canada.
dark energy ✔️The general term for the substance that causes the universe to expand at an
accelerated rate. Although it is believed to be 74 percent of the total energy in the universe, we know
very few of its properties. One active area of research is to determine whether it behaves like the
cosmological constant or changes over time.
dark matter ✔️A form of matter unlike the ordinary matter that is described by the Standard Model. It
accounts for most of the mass in the universe, but only has been observed indirectly through its
gravitational influence on ordinary matter. Is believed to account for 23 percent of the total energy in
the universe.
electron accelerator ✔️A particle accelerator designed to accelerate electrons.
gamma rays ✔️High-energy photons that are sometimes emitted from the nucleus of an atom that has
just decayed by emitting an alpha or a beta particle. Typically have energies greater than 1 MeV. They
are on the high-energy end of the electromagnetic spectrum.
gluons ✔️Particles in the Standard Model that mediate strong interactions. Because they carry color
charge, they can participate in the strong interaction in addition to mediating it. The term comes directly
from the word glue, because they bind together into mesons.
hadron ✔️A Standard Model particle made of quarks. Mesons and baryons are classified as these
particles.
Higgs boson ✔️A Standard Model "God" particle thought to give particles their mass. Light particles
interact less strongly with these than heavy particles. As of 2010, it had not yet been discovered. If it
exists, experiments at LEP and the Tevatron have determined that its mass cannot be smaller than 110
GeV, and cannot lie between 163 and 166 GeV.
kaon ✔️Refers to any one of four mesons with nonzero strangeness. The positively charged K+ is
composed of an up quark and an anti-strange quark. Its antiparticle is the negatively charged K- ,
which is composed of an anti-up quark and a strange quark. The two neutral ones, and are made
