Radiation, as used in physics, is energy in the form of waves or moving subatomic particles emitted by an atom or other body as it changes from a higher energy state to a lower energy state. Radiation can be classified as ionizing or non-ionizing radiation, depending on its effect on atomic matter. The most common use of the word "radiation" refers to ionizing radiation. Ionizing radiation has enough energy to ionize atoms or molecules while non-ionizing radiation does not. Radioactive material is a physical material that emits ionizing radiation.

This shows three different types of radiation and their penetration levels

Types of Radiation

There are three types of radiation, alpha, beta and gamma radiation. They are all emitted from the nucleus of an unstable atom.

Effects of electromagnetic fields

Positively charged alpha particles are deflected by both magnetic and electric fields. Negatively charged beta particles are also deflected by both types of fields, but in the opposite direction from alpha particles. Neutrons and electromagnetic radiation have no charge, and consequently, are unaffected by electromagnetic fields.

Discovery

Wilhelm Roentgen is credited for the finding of X-Rays and Marie Curie discovered that only certain elements gave off these rays of energy. She called it radioactivity. She devoted much of her life to studying these rays, building on Henri Becquerel's finding of a very 'energetic" element called uranium, that gave off these rays.

In December of 1898, Marie Curie and Pierre Curie discovered radium in pitchblende. This new element was two million times more radioactive than uranium as described by Marie.

See also