O-LevelPhysicsNuclear Physics5054/12 · May/June 2015 · Q401 Mark

The half-life of a radioactive isotope is 24 hours. A sample of this isotope produces an initial count rate of 720 counts per second. How long does it take for the count rate to fall to 90 counts per second?

A3 hours

B72 hours

C96 hours

D192 hours

✓ Correct answer

B: 72 hours

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Topic: Nuclear Physics, O-Level Physics (syllabus 5054). Multiple choice, 1 mark.
Source: O-Level Physics, May/June 2015 Paper 1 Variant 2, question 40.

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