Essentials of Radiographic Physics and Imaging: Electromagnetic and Particulate Radiation

Vocabulary flashcards covering the properties of electromagnetic radiation, the electromagnetic spectrum, wave mechanics, inverse square law calculations, and particulate radiation.

Electromagnetic Radiation

An electric and magnetic disturbance traveling through space at the speed of light ($3 \times 10^8\,\text{m/s}$) that originates from the atom, vibrates as pure energy, and can travel through a vacuum.

Electromagnetic Spectrum

A continuum ordering or grouping of electromagnetic radiations that all travel at the same velocity ($3 \times 10^8\,\text{m/s}$) and vary only in energy, wavelength, and frequency.

Wavelength

The physical distance from one peak of a wave to another, spanning a range from $10^6$ to $10^{-16}\,\text{m}$ across the electromagnetic spectrum.

Amplitude

The height of an electromagnetic wave.

Frequency

The number of waves passing a given reference point per second, measured in hertz ($\text{Hz}$).

Electromagnetic Wave Velocity Equation

The relationship defined by $\text{Velocity} = \text{frequency} \times \text{wavelength}$, meaning frequency and wavelength are always inversely related because velocity is constant.

Direct Relationship

A graphical relationship wherein the value of the Y-axis increases as the value of the X-axis increases.

Inverse Relationship

A graphical relationship wherein the value of the Y-axis decreases as the value of the X-axis increases.

Wave-Particle Duality

The concept that electromagnetic radiation exhibits characteristics of either a wave or a particle depending on its energy and environment.

Inverse Square Law

The principle stating that the intensity of radiation diminishes by a factor of the square of the distance from the source.

Ionization

The process by which a photon or particle with sufficient energy removes an orbital electron from an atom during an interaction.

Ion Pair

The atom and the electron that was removed from it following an ionization event.

Radio Waves

The lowest-energy members of the electromagnetic spectrum, used medically in magnetic resonance imaging (MRI), that do not ionize atoms.

Microwaves

Low-energy electromagnetic waves used to transmit cell phone signals and heat food that can cause tissue heating but cannot ionize atoms.

Infrared Light

A non-ionizing form of electromagnetic radiation sometimes used to beam information between electronic devices.

Visible Light

The tiny, non-ionizing portion of the electromagnetic spectrum that represents the colors humans can visually perceive.

Ultraviolet Light

Electromagnetic radiation approaching the energies of X-rays that stimulates melanin production and can cause skin cancer, but lacks the energy to ionize atoms.

Particulate Radiation

Subatomic particles, such as alpha particles and beta particles, that possess sufficient kinetic energy to ionize matter.

Radioactivity

The process (also known as radioactive decay) by which an atom containing excess energy in an unstable nucleus emits particles and energy to regain stability.

Half-life

The length of time required for half the remaining unstable atoms in a quantity of a radioactive element to decay.

Alpha Particle

A particulate radiation particle composed of two protons and two neutrons (identical to a helium nucleus) with a net positive charge and low penetrating ability.

Beta Particle

A fast, light particulate radiation particle consisting of an electron emitted directly from an unstable nucleus rather than an orbital shell.

Positron

A positively charged beta particle emitted from an unstable atomic nucleus.