Absorption is the transformation of the energy of radiation (x-rays) into another form.

Alloy is a composition of two or more metals.

Angiogram is a picture of one or more blood vessels which are filled with X-ray dye.

Atomic Number is the number of protons in the nucleus. (This is equal to the number of electrons in orbit around the nucleus in a neutral atom.

Background radiation refers to the low intensity radiation due to cosmic rays and naturally occuring radioactive material.

Barium This is a chalky liquid which outlines various parts of the digestive tract on an X-ray. It is inert and is not absorbed by the body. A patient may drink it to enable an x-ray study of their esophagus, stomach or small intestine.

Bremsstrahlung is electromagnetic radiation (usually x-rays) produced by the rapid deceleration of an electron which passes close to a nucleus (translates as "braking radiation").

Casting is the process of shaping molten metals in a mould.

CAT scan This is short for Computer Assisted Tomography. This technique uses X-rays to generate computerized images (pictures) of all parts of the body. The technique can create three-dimensional pictures. (Sometimes referred to as CT scan, for Computer Tomography).

Cathode rays are electrons emitted from the negatively charged plate in a discharge tube.

Cathode Ray Tube is a vacuum tube which allows the direct observation of cathode rays (e.g. a television tube).

Compton Effect is the reduction in energy of a photon, as a result of its interaction with an electron.

Contrast A substance which is apaque to x-rays, used during an X-ray examination. It can be given orally or intravenously (by injection).

Crystal is a solid material whose atoms are arranged in a precise pattern.

Crystallography is the study of the structure of crystals.

Diffraction is the spreading of a wave after passing through a gap of comparable dimensions to the wavelength of the wave

Discharge tube is a partially evacuated tube in which electrons travel whenever a suitable voltage is applied between the electrodes in the tube.

Elastic scattering is the result of elastic collisions where the particles which collide do not lose energy due to the collisions.

Electromagnetic waves are caused by the acceleration of charged particles. These waves involve electric and magnetic fields vibrating transversely and sinusoidally at right angles to the direction that the wave is travelling. The waves do not require a medium for propogation and travel through a vacuum at 300 million meters per second.

Dose the amount of energy deposited per unit mass.

Electron is a tiny particle which has negative charge.

Film badges contain photographic film and are usually worn by workers who are in regular contact with ionizing radiation. The badge indicates the extent of their exposure to ionising radiation.

Fluorescent materials are those which emit light when radiation strikes them.

Frequency is the number of oscillations (cycles) per second (measured in hertz).

Glancing angle is the angle between a ray and the reflecting surface.

Hard X-rays are those of high frequency and therefore high penetrating ability.

Hertz (Hz) is a unit of frequency; equal to one oscillation per second.

Induction Coil is a device for producing high voltages from low voltage direct current, using electromagnetic induction.

Intensity is the amount of energy passing through unit area normal to the direction of the wave.

Ion is a charged atom

Ionisation is the process of forming ions
(It often involves the removing of electrons from atoms).

Ionization chamber is a device for measuring the amount of ionizing radiation.

Ionizing radiation has sufficient energy to interact with atoms and remove electrons from their orbits, causing the atom to become charged or "ionized."

Irradiated means exposed to radiation.

KE is Kinetic Energy which is the energy a body has by virtue of its motion.

keV is a kilo-electron Volt (1000 electron volts) and is a measure of energy applicable to sub-atomic particles.

Lattice is a regular network of fixed points about which the atoms or molecules vibrate in a crystal.

Linear Accelerator is a collection of cylindrical electrodes used to accelerate charged particles to high energies.

Mammogram is an X-ray of the breast. It is used to detect breast cancer and other abnormalities of the breast.

MeV is a million electron volts.

Monochromatic one colour (i.e. waves of a single wavelength i.e. of a single frequency)

Mutation refers to a change in the chemical constitution of the chromosomes of an organism.

Nanometer is ten to the power of minus nine of a meter (one millionth of a milli-meter).

Nucleus is the positively charged core of an atom.

Opaque means not permitting certain types of wave motion to pass through.

Pair Production refers to the creation of an electron and a positron as a result of a photon of radiation passing close to a nucleus.

PE is Potential Energy which is the energy a body has by virtue of its position.

Photodiode is a semiconductor component whose conductivity is modulated by the absorption of light.

Photoelectric effect is the emission of electrons from the surface of a metal when light of sufficiently short wavelength is incident on the metal.

Photons may be thought of as bundles of energy. The amount of energy in a photon is proportional to the frequency of the radiation.

Polarized radiation is where the electric and magnetic oscillations are confined to one plane (rather than three-dimensional).

Positron is a particle with the same mass as an electron but with a positive charge (equal in magnitude to that of an electron).

Quantum Mechanics is the branch of physics that interprets physical phenomena occuring on a very small scale (e.g. the motion of electrons).

Radiation is defined as the emission and propagation of energy in the form of rays, waves or particles through a medium. Examples include radio waves, microwaves, visible light, ultraviolet, x-rays and cosmic rays.

Radiation dose is the amount of energy deposited per unit mass of matter.

Radiation therapy This is where large doses of X-rays are used to treat cancer by killing cancer cells.

Radioactivity is the spontaneous disintegration of the nucleus of certain elements with the consequent emission of radiation. (The chemical nature of the original atom is changed in the process).

Radiologist A doctor who interprets X-ray images to diagnose disease.

Radiology In general, "radiology" refers to medical imaging techniques that allow doctors to see inside a patient's body. Although the word "radiology" implies radiation, not all of the techniques actually use radiation.

Refract means that a ray changes direction as it passes from one medium to another of different density.

Scan This is a term used to describe the computerized images (pictures) generated by computer assisted tomography.

Sievert is the SI unit of dose equivalent being that arising when the absorbed dose of ionising radiation is one Joule per kilogram.

Soft X-rays are those of relatively low frequency and therefore low penetrating ability.

Spectrometer is an instrument used for measuring the wavelength of radiation.

Spectrum is a display of colours (as in the rainbow). It may also refer to a distribution of radiation after it has been diffracted.

Thermionic emission is the emission of electrons from the surface of a metal when the metal is heated.

Tomography is a technique for using x-rays for photographing one specific plane of the body, for diagnostic purposes.

Tungsten is a metal with atomic number 74 and a melting point of 3410 C.

Vacuum Pump reduces the pressure of a gas in a container by extracting some of the gas.

Voltage is a measure (in volts) of the potential difference between two parts of an electrical circuit.

Wave is a transmission of energy.

Wavelength is the distance between two successive crests.

Weld is a joining of two metal surfaces by heating sufficiently to melt them together.