1. Half Life Physics 2 Additional Science Chapter 13

2. The time radioactivity takes to reach half its dose What is “Half Life”? The time taken for half the radioactive atoms to decay OR Additional Science Chapter 13

3. Number of popcorn left 16 12 8 4 0 0 10 20 30 40 50 Time (seonds) Half-life of the popcorn = 10s Example of half-life, using a pan of popping popcorn Additional Science Chapter 13

4. 20s40s 30s 10s 50s 0sExercise Number of popcorn left 32 24 16 8 0 0 20 40 60 80 100 Time (seconds) Half life of the popcorn = 20s The half life of the popcorn is 20s The sample contains 32 popcorn at the start. How many will be left after 60s? ? Answer = 4 Additional Science Chapter 13

5. Number of nuclei remaining 480 360 240 120 0 0 433 866 1299 1732 2165 Time (years) 1. How many will be left after 1300 years? 2. How many years will have passed before it is harmless? Nuclei 480 240 120 60 30 16 8 Years 433 433 433 433 433 433 Question on half life Answer1 Answer 2 Explanation Half Life 1 2 3 4 5 6 1. 60 nuclei 2.6 x 433 years = 2598 years The half life of americium is 433 years. The example contains 480 nuclei. Additional Science Chapter 13