Quantum Physics For Dummies, Revised Edition

Glossary

Here’s a glossary of common quantum physics terms:

amplitude: The maximum amount of displacement of an oscillating particle.

angular momentum: The product of the distance a particle is from a certain point and its momentum measured with respect to the point.

annihilation operator: An operator that lowers the energy level of an eigenstate by one level.

anti-Hermitian: An operator whose Hermitian adjoint is the same as the original operator, but with a minus sign; in other words, an operator is anti-Hermitian if A† = –A. See also Hermitian operator.

black body: A body that absorbs all radiation and radiates it all away.

Bohr radius: The average radius of an electron’s orbit in a hydrogen atom, about 10–10 meters.

bound state: A state in which a particle isn’t free to travel to infinity.

bosons: Particles with integer spins, including photons, pi mesons, and so on.

bra-ket notation: Abbreviating the matrix form of a state vector as a ket, or |ψ>, and abbreviating the ket’s complex conjugate, or bra, as <ψ|.

center-of-mass frame: In scattering theory, the frame in which the center of mass is stationary and the particles head toward each other and collide. See also lab frame.

central potential: A spherically symmetrical potential.

commute: Two operators commute with each other if their commutator is equal to zero. The commutator of operators A and B is [A, B] = AB – BA.

complex conjugate: The number you get by negating the imaginary part of a complex number. The * symbol ...