Edexcel iGCSE Physics -7.6 Core Practical: Radiation Penetration- Study Notes- New Syllabus

Practical: Investigating the Penetrating Power of Radiation

This practical investigates the penetrating power of alpha (α), beta (β⁻), and gamma (γ) radiation by measuring how different materials reduce the detected count rate.

Aim

To compare the penetrating power of alpha, beta, and gamma radiation using absorbing materials.

Apparatus

• Radioactive sources (α, β, γ) or computer simulation
• Geiger–Müller tube and counter
• Absorbing materials:
  • Paper
  • Aluminium sheets
  • Lead sheets
• Ruler (cm)
• Stopwatch (s)

Method

• Place the radioactive source a fixed distance from the detector.
• Measure the background radiation for a fixed time.
• Record the initial count rate with no absorber.
• Place a sheet of paper between the source and detector and record the count rate.
• Repeat using increasing thicknesses of aluminium.
• Finally, repeat using lead sheets.
• Keep distance and time constant throughout.

Alternative (Simulation): Use an online radiation simulation to insert absorbing materials and record count rates.

Results and Observations

• Paper stops alpha radiation completely.
• Aluminium reduces beta radiation significantly.
• Gamma radiation is only reduced by thick lead.

Conclusion:

• Alpha → least penetrating
• Beta → moderately penetrating
• Gamma → most penetrating

Safety Precautions

• Use tongs to handle radioactive sources.
• Never point sources at people.
• Store sources in lead-lined containers.
• Limit exposure time.

Key Sources of Error and Improvements

• Background radiation → subtract background count.
• Detector movement → fix positions securely.
• Short counting times → use longer times to reduce random error.