HKDSE Radioactivity

Random Nature of Radioactive Decay

It cannot be predicted when a particular unstable nucleus will decay, but the probability of decay in a time interval can be estimated.

Key idea

  • • Every undecayed nucleus has the same probability of decay.
  • • We cannot know which nucleus will decay next.
  • • Temperature, pressure and chemical state do not change the decay rate.

GM tube count-rate fluctuations

Reset the counter, wait one minute, then record the count. Repeated readings fluctuate randomly.

Latest count
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Mean of readings
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Recorded readings
32, 11, 25, 16, 28