# Video: Understanding Activity and Half-Life

The initial activity of a sample of radioactive material is 1200 Bq. What is the activity of the sample after 1 half-life has passed?

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### Video Transcript

The initial activity of a sample of radioactive material is 1200 becquerel. What is the activity of the sample after one half-life has passed?

Alright, so in this question, we’ve been told first of all the initial activity of a sample of radioactive material. And we know that this value is twelve hundred becquerel or 1200 becquerel. What we’ve been asked to do is to find the activity of the sample after one half-life has passed.

To answer this question, we first need to know what half-life actually means. A half-life is defined as the amount of time taken for the radioactivity of a sample to drop to half its initial value. So in this situation, if we’ve got a sample which has an initial activity of 1200 becquerel.

So in this situation, if we have a sample that has an initial activity of 1200 becquerel, then after one half-life has passed the activity of the sample is going to be half of 1200 becquerel.

In other words, the activity after one half life is past is going to be 1200 divided by two becquerel. And 1200 divided by two is 600. So the activity of the sample after one half-life has passed is 600 becquerel.