1. Do Now Copy and complete : page 265 The ________ of a radioactive substance is the average time taken for half of the _______of the substance to decay. It is also equal to the average time taken for the ________ of the substance to halve. The half-life of carbon 14 is about _______ years. If today a sample of carbon 14 has an activity of 3400 Bq then in 5600 years time this should have fallen to ______ Bq. 11200 years later the activity should have fallen to ____ Bq. The number of carbon 14 nuclei would have also decreased by ______ times. eighthalf-life5600425activity1700 WORD & NUMBER SELECTION: nuclei eight half-life 5600 425 activity 1700 nuclei

2. Today’s lesson Find the half life from graphs version 2. Give and explain examples of practical applications of isotopes. Title Uses of radioactive isotopes

3. Finding half-life from a graph half-life The half-life in this example is about 30 seconds. A more accurate value can be obtained be repeating this method for a other initial nuclei numbers and then taking an average.

4. Question 6 Estimate the half-life of the substance whose decay graph is shown opposite. half-life

5. Revision Simulations Half-LifeHalf-Life - S-Cool section on half-life and uses of radioactivity including an on- screen half-life calculation and an animation showing thickness control. BBC AQA GCSE Bitesize Revision: Detecting radiation Natural sources of background radiation Artificial radiation Half life Alpha DecayAlpha Decay - PhET - Watch alpha particles escape from a Polonium nucleus, causing radioactive alpha decay. See how random decay times relate to the half life.

6. Title Uses of radioactive isotopes

7. Smoke detection Uses

8. Thickness control

10. Used as Tracers

12. Killing microbes

14. Checking welds

15. Used as TracersTracers

16. Carbon dating

17. “Can you………?” Bring in your exercise books on Thursday 27 th Sept.

18. Test! Thursday 27 th September 2012 I will collect your Exercise books on Thursday – Remember them!

19. Can you answer the all the questions on pages 265 and Q5,7,8,9 &10 page 270?