Exam-style question
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During an absorption experiment, a beta emitter is placed behind a sheet of aluminium. What is the most likely observation as the aluminium thickness is increased?.
- A.The beta count rate increases because aluminium accelerates the beta particles.
- B.The beta count rate remains constant because aluminium is transparent to beta particles.
- C.The beta count rate decreases gradually and then sharply as the particles are stopped.
- D.The beta count rate oscillates due to interference effects.
Model answer
What a good answer should say
- The beta count rate decreases gradually and then sharply as the particles are stopped.
Explanation
Why this works
Beta particles are electrons or positrons that lose energy through ionisation and scattering. As the aluminium thickness increases, more beta particles are slowed and stopped before reaching the detector, leading to a gradual reduction in count rate that becomes steep when the thickness exceeds the range of the beta particles.
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