PHYSICS
TOPIC: RADIATION & THE TYPES OF
RADIATION
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)
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Alpha Particle
Alpha radiation consists of
alpha particles. An alpha
2 protons particle is identical to the
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