Q. A radio isotope has an initial activity of 840 Bq (Becquerel = 1 radioactive / nuclear decay per second). What will the activity of the sample be after 5 half lives, as a percentage of the original?.


Q. A radio isotope has an initial activity of 1200Bq, after 7 hours it has decreased to 4.6875 Bq. What is the half life of the isotope?


Q. A sample of Caesium-137 is found to have an activity of 24 Bq. Caesium-137 has a half-life of 30 years. What will the activity be, in Bq, at 90 years?


Q. Caesium-137 decays to an isotope of Barium-137. From this information alone, suggest the type of decay taking place. Show the equation for your decision.


Q. The half life of a radioactive isotope is 27 years. How long will it take for a 2g sample of the isotope to reduce in mass to 0.25g ?


Q. The activity of an isotope falls from 600 Bq (becquerel) to 150 Bq in 10 days. What is its half-life?


Q. An isotope has a half-life of 30 years. Estimate how long it will take for the number of nuclei to decay to below 200 if the starting number is 8,000?


Q. A radioactive isotope has a half life of 30 minutes, what fraction of the substance will NOT have decayed after 1 hour?


Q. A substance has a half life of 3 hours, what fraction of a sample will have decayed after 6 hours?


Q. A scientist records an activity of  200 counts per minute coming from a radioactive source. This measurement takes place at 12:00pm. At 3.pm she takes another reading which is 25 counts per minute. What is the half life of the substance?




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