Radiologic Technology Board Exam Review: Radiation Physics and Characteristics

Comprehensive practice vocabulary flashcards covering the core concepts of Radiation Physics based on the board exam review transcript.

Matter

Anything that occupies space and has mass; the material substance that makes up physical objects.

Mass

The amount of matter contained in an object, measured in kilograms ($kg$), which remains constant regardless of location or gravity.

Weight

The force exerted on an object due to gravity, which depends on the strength of the gravitational field acting on the object.

Energy

The ability to do work, measured in joules ($J$) or electron volts ($eV$) in radiology.

Electron Volt ($eV$)

The energy gained by an electron when it moves through a potential difference of $1$ volt ($V$); $1\,eV = 1.602 \times 10^{-19}\,J$.

Potential Energy

Energy stored because of an object's position.

Kinetic Energy

The energy of motion.

Electrical Energy

Energy produced when electrons move through an electric potential difference or voltage.

Thermal Energy

The energy of motion at the molecular level, where faster vibration results in higher temperature.

Electromagnetic Energy

A form of energy that includes radio waves, microwaves, visible light, and x-rays, which is central to the field of radiology.

Atom

The smallest particle of an element that retains its chemical properties, consisting of a dense nucleus surrounded by orbiting electrons.

Plum Pudding Model

The atomic model proposed by J.J. Thomson where electrons are embedded in a sphere of positive charge.

Nuclear Model

Ernest Rutherford's model describing the atom as having a small, dense, positively charged center called the nucleus.

Bohr Atom

A model proposed in 1913 describing electrons moving around the nucleus in fixed paths called orbits or energy levels, similar to a solar system.

Nucleons

The protons and neutrons found inside the nucleus, which are composed of smaller subnuclear particles called quarks.

Proton

A positively charged subatomic particle found in the nucleus with a relative mass of about $1836$ times heavier than an electron; its discovery is associated with Eugen Goldstein.

Neutron

A neutral subatomic particle found in the nucleus, discovered by James Chadwick, that is slightly heavier than a proton.

Electron

A negatively charged particle that orbits the nucleus with a mass of approximately $9.1 \times 10^{-31}\,kg$.

Atomic Mass Unit ($amu$)

A unit equal to one-twelfth of the mass of a carbon-12 atom, used to express the mass of atomic particles.

Principal Quantum Number ($n$)

The number used to identify electron shells (K=1, L=2, M=3, etc.).

$$2n^2$$

Pauli's exclusion formula used to determine the maximum number of electrons that can occupy a specific electron shell.

Octet Rule

The principle that the outermost shell of an atom usually does not exceed $8$ electrons, at which point the atom becomes chemically stable and inert.

Valence

The combining power of an atom, determined by the number of electrons in its outermost shell.

Ionic Bond

A chemical bond formed when one atom gives up an electron and another atom accepts it, such as in sodium chloride ($NaCl$).

Covalent Bond

A chemical bond formed when atoms share electrons, such as the bond between hydrogen and oxygen in water ($H_2O$).

Centripetal Force

The electrostatic attractive force that pulls negative electrons toward the positive nucleus, keeping them in orbit.

Centrifugal Force

The "flying-out" effect created by electrons moving in a circular path that pushes them away from the nucleus.

Electron Binding Energy ($E_b$)

The strength of attachment of an electron to the nucleus, representing the energy required to remove an electron from the atom.

Atomic Number ($Z$)

The number of protons in the nucleus of an atom, which identifies the element.

Atomic Mass Number ($A$)

The total number of protons and neutrons in an atom's nucleus.

Isotopes

Atoms of the same element that have the same atomic number but different atomic mass numbers (same protons, different neutrons).

Isobars

Atoms that have the same atomic mass number ($A$) but different atomic numbers ($Z$).

Isotones

Atoms that have the same number of neutrons but different numbers of protons.

Isomers

Metastable atoms that have the same atomic number and mass number but exist at different nuclear energy states.

Radiation

Energy emitted and transferred through matter or space.

Particulate Radiation

Radiation composed of tiny moving particles that possess mass and may carry an electric charge, such as alpha and beta particles.

Alpha Particle

A particle identical to a helium nucleus ($2$ protons and $2$ neutrons) with a $+2$ charge and high ionizing ability, but a very short range in matter.

Beta-Minus Particle ($\beta^-$)

Also known as a negatron, it is an electron emitted from the nucleus during radioactive decay when a neutron changes into a proton.

Beta-Plus Particle ($\beta^+$)

Also known as a positron, it is the antiparticle of the electron with a positive charge, emitted from the nucleus during radioactive decay.

Photon

The smallest quantity or "packet" of electromagnetic energy, having no mass and no electric charge.

Wavelength ($\lambda$)

The distance between two identical points on a wave, such as crest to crest, measured in units like angstroms ($\mathring{A}$) or meters.

Frequency ($\nu$)

The number of wave cycles that pass a point every second, measured in hertz ($Hz$).

Wave Equation

The relationship where velocity equals frequency times wavelength ($c = f \lambda$); since the speed of light is constant, frequency and wavelength are inversely proportional.

Planck's Constant ($h$)

A value ($4.15 \times 10^{-15}\,eV \cdot s$) used to relate photon energy and frequency in the formula $E = h \nu$.

Gamma Rays ($\gamma$)

High-energy electromagnetic photons that originate from the nucleus of a radioactive atom.

X-rays

Electromagnetic photons produced outside the nucleus, usually in the electron cloud, through interactions with target atoms.

Ionization

The process by which an electron is completely removed from an atom, resulting in an ion pair consisting of a free electron and a positive atom.

Excitation

A process where an electron is raised to a higher energy level but not removed from the atom, which may produce heat.

Directly Ionizing Radiation

Charged particles (alpha, beta, protons) that interact directly with orbital electrons through electrostatic interactions.

Indirectly Ionizing Radiation

Uncharged radiation (x-rays, gamma rays, neutrons) that must first interact with matter to produce charged particles, which then cause ionization.

Radon

The largest source of natural environmental radiation, which emits alpha particles and contributes radiation dose mainly to the lungs.

Radioactivity

The phenomenon where an unstable nucleus releases energy and particles to become stable, measured in disintegrations per unit time.

Becquerel ($Bq$)

The SI unit of radioactivity, where $1\,Bq = 1$ disintegration per second.

Curie ($Ci$)

A unit of radioactivity equal to $3.7 \times 10^{10}$ disintegrations per second.

Annihilation

The process occurring when a positron interacts with an electron, resulting in their mutual destruction and the production of two $0.511\,MeV$ photons.

Isomeric Transition

A decay process where an excited nucleus in a metastable state releases excess energy as gamma rays or internal conversion electrons to move to a lower-energy state.

Physical Half-Life ($T_{1/2}$)

The time required for a radioactive material to decrease to one-half of its original activity by radioactive decay alone.

Effective Half-Life

The actual time it takes for radioactive material in the body to decrease by half, combining both physical decay and biological excretion.

Linear Energy Transfer (LET)

The amount of energy deposited by radiation per unit length of its path, usually expressed in $eV/cm$ or $keV/\mu m$.

Characteristic Radiation

X-rays produced when an outer-shell electron fills an inner-shell vacancy, with energy exactly equal to the difference in shell binding energies.

Auger Electron

An electron ejected from the atom using energy transferred directly from an electron transition, instead of the energy being released as a characteristic x-ray.

Bremsstrahlung Radiation

Meaning "braking radiation," it is produced when a projectile electron is slowed down and diverted by the nuclear force field, emitting its lost kinetic energy as a photon.

Attenuation

The reduction in the number of x-ray photons and loss of energy as a beam passes through matter due to absorption and scattering.

Coherent Scattering

Also called classical or unmodified scattering, it occurs at low energies ($< 10\,keV$) where the incident photon changes direction without losing energy or causing ionization.

Compton Scattering

An interaction where an incident photon partially transfers energy to an outer-shell electron (recoil electron) and continues in a different direction with reduced energy.

Photoelectric Effect

The total absorption of an incident x-ray photon by an inner-shell electron, resulting in the ejection of a photoelectron and the creation of a characteristic x-ray.

Pair Production

An interaction requiring at least $1.02\,MeV$ where a photon is converted by the nuclear field into an electron and a positron.

Photodisintegration

A high-energy interaction ($> 10\,MeV$) where a photon is absorbed by the nucleus, which then emits a nucleon or nuclear fragment.