Group Assignment Physics Topic: Radiation & The types of Radiation Group 1 History of Radiation – In 1986 Henri Becquerel noticed that, after leaving a sample of uranium in a drawer near some photographic film, the film became exposed. He theorized that the uranium was producing ‘invisible rays’ which caused a chemical reaction in the film. Over the next few years, Marie and Pierre Curie investigated other minerals and isolated radium in sufficient amounts to allow the study of its properties. What is Radiation? – Radiation is the emission or transmission of energy through waves or particles through space or a material medium. Background Radiation Background radiation is emitted from both naturally occurring and man-made sources. Natural sources include cosmic radiation, radon, radiation in the body, solar radiation, and external terrestrial radiation. Manmade forms of radiation are used in X-rays, cancer treatment, nuclear facilities, and nuclear weapons. It can also come from unstable atoms that undergo radioactive decay. Types of Radiation – There are three main types of ionizing radiation emitted from the unstable nuclei of radioactive atoms. These are alpha, beta, and gamma radiation. Helium Atom Alpha Radiation (α) • • • Alpha Particle Alpha radiation consists of alpha particles. An alpha particle is identical to the 2 protons 2 neutrons nucleus of a helium atom, 2 electrons which comprises two protons and two neutrons. • 2 protons • 2 neutrons • 0 electrons Beta Radiation (β) Beta radiation consists of high-energy electrons emitted from the nucleus. These electrons have not come from the electron shells or energy levels around the nucleus. Instead, they form when a neutron splits into a proton and an electron. The electron then shoots out of the nucleus at high speed, leaving the new proton behind in the nucleus. Gamma radiation (γ) Gamma radiation is very short wavelength, high frequency electromagnetic radiation. This is similar to other types of electromagnetic radiation, such as visible light and X-rays, which can travel long distances. Features of the types of Radiation Penetrating Properties of the Types of Radiation Alpha radiation Alpha radiation is the least penetrating. It can be stopped (or absorbed) by a sheet of paper or a human hand. Beta radiation Beta radiation can penetrate air and paper. It can be stopped by a thin sheet of aluminium. Gamma radiation Gamma radiation is the most penetrating. It can penetrate air, paper or thin metal. It may only be stopped by many centimetres of lead or many metres of concrete. Alpha, beta and gamma rays passing through a hand, beta and gamma rays passing through aluminium and gamma rays stopping at lead. Questions – What is radioactive emission? – Who discovered radiation? – What are the types? – Atoms with unstable nuclei are said to be__. – Particles including two protons and two neutrons bound together are known as_____. Answers – Radiation is the emission or transmission of energy through waves or particles through space or a material medium. – Was discovered in 1896 by scientists Henri Becquerel and Marie Curie. – Alpha, beta and gamma radiation. – Radioactive – Alpha