1. The half-life of the element in this table is 5700 years. This is determined by observing that the activity decreases from 10000 Bq to 5000 Bq in 5700 years, which is a halving of the initial activity, indicating one half-life.
2. The half-life of the element in this table is 10 seconds. This is determined by observing that the activity decreases from 200 Bq to 100 Bq in 10 seconds, which is a halving of the initial activity, indicating one half-life.
3. After three half-lives, 875 radioactive nuclei would be decayed. This is calculated as follows: After one half-life, 500 nuclei remain (1000 - 500 = 500 decayed). After two half-lives, 250 nuclei remain (500 - 250 = 250 decayed). After three half-lives, 125 nuclei remain (250 - 125 = 125 decayed). Therefore, the total number of decayed nuclei is 1000 - 125 = 875.
4. Three half-lives have passed. This is determined by observing that the remaining activity is 175 out of an initial 2800. After one half-life, 1400 remain. After two half-lives, 700 remain. After three half-lives, 350 remain. After four half-lives, 175 remain. Therefore, four half-lives have passed.
Parent Tip: Review the logic above to help your child master the concept of half life calculations worksheet.
