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DETECTION OF NUCLEAR
RADIATION
11.03
BACKGROUND RADIATION
• There is a small amount of radiation around us
because of radioactive materials in the
environment. This is called background
radiation. The sources are;
• Ground and buildings
• Granite rocks- radon gas
• Medical
• Cosmic rays from space,
• nuclear test fallout, power stations, waste etc.
GEIGER MULLER (GM) TUBE
• Used to detect alpha, beta and gamma
radiations
• The window is thin enough to allow
radioactive particles to enter
• when radioactive particles enter the tube,
the gas inside is ionized
• This sets off a high voltage spark and
sends a pulse of current in the circuit
• A ratemeter: gives the reading in counts
per second
• A scaler: counts the total number of
particles detected by the tube
• An amplifier & loudspeaker: makes a click
when each particle or burst of gamma
radiation is detected
• The average reading of the background
radiation must be found first and then
subtracted from the total reading to get the
radiation from a source.
Cloud chamber
• It consists of a chamber with cold alcohol
vapour in the air inside it
• When alpha particles enter the chamber,
the vapour condenses and a trail of tiny
droplets are seen where each particle
passes through
CLOUD CHAMBER