1. Friday Dec 12 Objective: Calculate the half-life of radioactive materials. Checkpoint: What is the half-life of a radioactive sample if it takes 10 years for a 100 gram sample to decay to 50 grams? Homework: – Study guide (due Tuesday beginning of class)

2. Half-Life The time it takes for half of a radioactive sample to decay. 100 g 50 g 10 years

3. Underground repository for used fuel (1650 ft underground)

4. Half-Life The time it takes for half of a radioactive sample to decay. The half-life of Iodine-131 is 8 days.

5. Half-Life The time it takes for half of a radioactive sample to decay. The half-life of Iodine-131 is 8 days. 8 days

6. Half-Life The time it takes for half of a radioactive sample to decay. The half-life of Iodine-131 is 8 days. 16 days

7. Half-Life The time it takes for half of a radioactive sample to decay. The half-life of Iodine-131 is 8 days. 24 days

8. Half-Life The time it takes for half of a radioactive sample to decay. The half-life of Iodine-131 is 8 days. 32 days

9. Half-Life The time it takes for half of a radioactive sample to decay. The half-life of Iodine-131 is 8 days. 40 days

10. Half-Life The time it takes for half of a radioactive sample to decay. The half-life of Iodine-131 is 8 days. 48 days

11. Half-Life The time it takes for half of a radioactive sample to decay. The half-life of radioactive Uranium-238 is 4.46 billion years.

12. Half-Life The time it takes for half of a radioactive sample to decay. The half-life of radioactive Uranium-238 is 4.46 billion years. 4.46 billion years

13. Half-Life The time it takes for half of a radioactive sample to decay. The half-life of radioactive Uranium-238 is 4.46 billion years. 8.92 billion years

14. Half-Life The time it takes for half of a radioactive sample to decay. The half-life of radioactive Uranium-238 is 4.46 billion years. 13.38 billion years

15. Half-Life The time it takes for half of a radioactive sample to decay. The half-life of radioactive Uranium-238 is 4.46 billion years. 17.84 billion years

16. Half-Life The time it takes for half of a radioactive sample to decay. The half-life of radioactive Uranium-238 is 4.46 billion years. 22.3 billion years

17. Half-Life The time it takes for half of a radioactive sample to decay. The half-life of radioactive Uranium-238 is 4.46 billion years. 26.76 billion years

18. 2) How much of a 100 grams of a radioactive sample is left after 50 years if its half life is 10 years? 100 g 50 g 1 half life (10 years) 25 g 2 half lives (20 years) 12.5 g 3 half lives (30 years) 6.25 g 4 half lives (40 years) 3.125 grams 5 half lives (50 years)

19. 5) What is the half-life of a radioactive sample if it takes 200 years for a 100 gram sample to decay to 25 grams? 100 g 50 g 25 g 1 half life 2 half lives 200 years Half-life = 200 / 2 = 100 years

20. 7) A radioactive sample has a half-life of 30 years. How many years must pass to reduce a 50 mg sample to 6.25 mg? 50 g 25 g 1 half life (30 years) 12.5 g 2 half lives (60 years) 6.25 g 3 half lives (90 years)

21. Radioactive Decay Lab

22. Trial # # isotopes 1 2 3 4 31 20 18 3 1234