Quiz 5.4 - Half-life calculations

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This quiz has 6 questions. Click Submit at the end to mark it. No personal data is collected.

1. An isotope has a half-life of 3 days. If it starts with a radioactivity of 80 Bq, how long will it take to drop to 10 Bq? *

1 point

3 days

6 days

9 days

12 days

2. An isotope has a half-life of 5 minutes. After 15 minutes its count rate is 30 Bq. What did it start at? *

1 point

60 Bq

90 Bq

120 Bq

240 Bq

3. An isotope's radioactivity drops from 200 Bq to 25 Bq in 12 seconds. What is the half-life of the isotope? *

1 point

2 s

3 s

4 s

5 s

4. The mass of undecayed atoms in a sample is 12 mg. The half-life is 7 hours. What will be the mass of undecayed atoms after 14 hours? *

1 point

3 mg

6 mg

12 mg

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