materials are composed of atoms that are unstable.
An unstable atom gives off excess energy until it
becomes stable. The energy the atom emits is
The process by which an atom changes from an
unstable state to a more stable state by emitting
radiation is called radioactivity.
Radiation can be
classified as either non-ionizing (low energy) or
ionizing (high energy) radiation. Types of
radiation are ultraviolet light,
visible light, infrared radiation, radio frequency
radiation and microwaves. Ionizing
radiation is given off by the sun
(cosmic rays), radioactive materials, and high
energy electronic devices (X-ray machines).
four major types of ionizing radiation.
charged particles made up of two neutrons and
two protons. They are relatively heavy
and slower moving than other radioactive
emissions. Alpha particles can be
stopped by a piece of paper or the dead
outer layer of our skin.
Particles are negatively charged
particles made up of an electron. A beta
particle is lighter and faster than an alpha
particle and can be stopped by a thin piece of
aluminium or a short span of air.
Rays are short wavelength
electromagnetic radiation emitted in the
radioactive decay of an unstable atom.
Gamma radiation is highly penetrating and is
stopped by lead.
are similar to gamma rays, but are
generally lower in energy and less
penetrating. X-rays are emitted from
processes outside the nucleus, while gamma
rays originate inside the nucleus.
A few milimeters of lead can stop medical
Nuclear Society Radiation Dose Chart
Office or Radiation and Indoor Air Radiation Protection
Division: Ionizing Radiation Series
Consumer Guide to Radon