Physics

# Key Terms

PhysicsKey Terms
activity
rate of decay for radioactive nuclides
alpha decay
type of radioactive decay in which an atomic nucleus emits an alpha particle
anger camera
common medical imaging device that uses a scintillator connected to a series of photomultipliers
atomic number
number of protons in a nucleus
becquerel
SI unit for rate of decay of a radioactive material
beta decay
type of radioactive decay in which an atomic nucleus emits a beta particle
carbon-14 dating
chain reaction
self-sustaining sequence of events, exemplified by the self-sustaining nature of a fission reaction at critical mass
critical mass
minimum amount necessary for self-sustained fission of a given nuclide
decay constant
quantity that is inversely proportional to the half-life and that is used in the equation for number of nuclei as a function of time
energy-level diagram
a diagram used to analyze the energy levels of electrons in the orbits of an atom
excited state
any state beyond the n = 1 orbital in which the electron stores energy
Fraunhofer lines
black lines shown on an absorption spectrum that show the wavelengths absorbed by a gas
gamma decay
type of radioactive decay in which an atomic nucleus emits a gamma ray
Geiger tube
very common radiation detector that usually gives an audio output
ground state
the n=1 orbital of an electron
half-life
time in which there is a 50 percent chance that a nucleus will decay
Heisenberg uncertainty principle
fundamental limit to the precision with which pairs of quantities such as momentum and position can be measured
hydrogen-like atom
any atom with only a single electron
isotope
nuclei having the same Z and different N’s
liquid drop model
model of the atomic nucleus (useful only to understand some of its features) in which nucleons in a nucleus act like atoms in a drop
mass number
number of nucleons in a nucleus
nuclear fission
reaction in which a nucleus splits
nuclear fusion
reaction in which two nuclei are combined, or fused, to form a larger nucleus
nucleons
particles found inside nuclei
planetary model of the atom
model of the atom that shows electrons orbiting like planets about a Sun-like nucleus
proton-proton cycle
combined reactions and that begins with hydrogen and ends with helium
amount of ionizing energy deposited per kilogram of tissue
substance or object that emits nuclear radiation
application of radioactive decay in which the age of a material is determined by the amount of radioactivity of a particular type that occurs
process by which an atomic nucleus of an unstable atom loses mass and energy by emitting ionizing particles
emission of rays from the nuclei of atoms
compound used for medical imaging
relative biological effectiveness (RBE)
number that expresses the relative amount of damage that a fixed amount of ionizing radiation of a given type can inflict on biological tissues
roentgen equivalent man (rem)
dose unit more closely related to effects in biological tissue
Rutherford scattering
scattering of alpha particles by gold nuclei in the gold foil experiment
Rydberg constant
a physical constant related to atomic spectra, with an established value of $1.097× 10 7 m −1 1.097× 10 7 m −1$
scintillator
radiation detection method that records light produced when radiation interacts with materials
strong nuclear force
attractive force that holds nucleons together within the nucleus
tagged
having a radioactive substance attached (to a chemical compound)
therapeutic ratio
the ratio of abnormal cells killed to normal cells killed
transmutation
process of changing elemental composition
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