Radiation Practical

• •  The aim of this experiment is to investigate the penetration powers of different types of radiation using either radioactive sources or simulations
• What are the control variables?

  • Radioactive source
  • Distance of GM tube to source
  • Location / background radiation
• What is the independent variable?

  Absorber material
• What is the dependent variable?

  Count rate
• Investigating radiation apparatus

  A)

  B) Storage for?

  C)

  D) Metal

  E) Metal

  F) Absorber

  G)

  
• What is step 1 of the practical?

  1. Connect the GM Tube to the counter and, without any sources present, measure background radiation over a one minute period
• What is step 2 of the practical?

  Repeat this three times, and take an average
• What is step 3 of the practical?

  Now place a radioactive source a fixed distance of 3 cm away from the tube and take another reading over a one minute interval
• What is step 4 of the practical?

  Now take a set of absorbers: some paper, several different thicknesses of aluminium (increasing in 0.5mm intervals) and different thickness of lead
• What is step 5 of the practical?

  One at a time, place these absorbers between the source and the tube and take another reading over a one minute interval
• What is step 6 of the practical?

  Repeat the above experiment for other radioactive sources
• If the count rate remains about the same when the material is inserted, the radiation can penetrate the material.
• If the count rate drops by a LARGE amount then the radiation is being absorbed and blocked by the material
• If the count rate drops by ZERO after the background count has been subtracted then the radiation is being completely absorbed.
• How to make the experiment more reliable?

  1. Make sure that the sources are stored well away from the counter during the experiment
  2. Conduct all runs of the experiment in the same location to avoid changes in background radiation levels
• The accuracy of an experiment is improved with using reliable sources with a long half-life and an activity well above the natural background level
• Safety considerations:

  1. Keep in lead-lined box, if radioactive sources not in use
  2. Pick up only using long-handled tongs or foreceps
  3. Keep safe distance
• What does the acronym SCREAMS stand for?

  • S: Which variable will you keep the same
  • C: which variable should you change
  • R: what will you do to make your experiment reliable
  • E: what special equipment and equations are required
  • A: how will you analyse your results
  • M: which variable will you measure
  • S: what safety precautions will you take?