Half-Life

Select the correction definition for half-life.

• The time it takes for all of the radioactive nuclei to decay.

• The time it takes for half of the radioactive nuclei to decay.

• Half the time it takes for all of the radioactive nuclei to decay.

• Half the time it takes for half of the radioactive nuclei to decay.

An alpha source in a smoke detector should have a _____ half-life.

The unit of activity is ____________.

A radioactive source has an activity of 800 Bq. It has a half-life of 4 hours. Calculate its activity after 24 hours.

A radioactive isotope has a half-life of 3 days. It's current activity 52 Bq. Calculate its activity 9 days ago.

The activity of a source is 680 Bq. After one full day its activity is has fallen to 85 Bq. Calculate its half-life.

The initial activity of a sample is 600 Bq. Calculate the percentage reduction in activity after 3 half-lives

The activity of a sample is 640 Bq. It's half-life is 3 hours. Calculate the percentage of activity remaining after 6 hours.

Use the half-life graph to calculate the half-life of the sample.

Calculate the activity of the sample after 3 half-lives.