An electromagnetic wave? Absorbed by a few cm of air? Alpha Beta Gamma An electromagnetic wave? Absorbed by a few cm of air? Stopped only by very thick lead? A fast moving electron? A large, positively charged particle? Stopped by aluminium? Stopped by paper?

Learning Objectives By the end of this lesson you should be able to… Describe the uses of different radioactive materials in the home and industry. Explain what is meant by the term ‘half-life’ of a radioactivity material. Describe why half-life is a useful tool when considering how to use radioactive materials.

Learning Objectives By the end of this lesson you should... Describe the uses of different radioactive materials in the home and industry. Explain what is meant by the term ‘half-life’ of a radioactivity material. Describe why half-life is a useful tool when considering how to use radioactive materials. Half-Life This is 1kg of uranium. It contains 2.56 X 1024 atoms of Uranium. Partly because there are so many and partly because radioactive decay is a random process it is impossible to tell exactly when any one atom of uranium might decay!

Learning Objectives By the end of this lesson you should... Describe the uses of different radioactive materials in the home and industry. Explain what is meant by the term ‘half-life’ of a radioactivity material. Describe why half-life is a useful tool when considering how to use radioactive materials. Half-Life Half-Life is a measure of how long it will take for half the atoms to have decayed (0.5kg). This gives us a wide margin of error and allows us to be much more precise!

Half-Life The half-life for U235 is 703 Million years. Learning Objectives By the end of this lesson you should... Describe the uses of different radioactive materials in the home and industry. Explain what is meant by the term ‘half-life’ of a radioactivity material. Describe why half-life is a useful tool when considering how to use radioactive materials. Half-Life The half-life for U235 is 703 Million years. This means after 703 million years 50% (half) the uranium will have decayed. After 1406 million years 75% quarters will have decayed. After 2109 million years 87.5% will have decayed.

Modelling Half-Life The decay of a radioisotope is completely random. – like the throw of a dice. We can not know when one will decay. But we do know, for a sample of the isotope, how long it will take for half the nuclides to decay.

No. of Throws No. of dice left 1 2 3 etc Roll all the dice, those that end up showing 6 have decayed. Remove them and record how many are left. Throw the remaining dice and repeat. No. of Throws No. of dice left 1 2 3 etc Plot, no. left against no. of throws. Draw a smooth curve.

Modelling Half-life Define the term ‘half-life’ Using your graph calculate the half-life (in turns) for your dice. If I start with 5,000 dice how many should I have left after 4 half-lives? What is this as a fraction of the original amount? If I have 2kg of Uranium what mass of uranium atoms will I be left with after 6 half lives.

Modelling Half-Life Learning Objectives By the end of this lesson you should... Describe the uses of different radioactive materials in the home and industry. Explain what is meant by the term ‘half-life’ of a radioactivity material. Describe why half-life is a useful tool when considering how to use radioactive materials. Modelling Half-Life

Half Life

Percentage of Carbon 14 (%) 100 75 50 25

Half-Life – What will we look at next? Learning Objectives By the end of this lesson you should... Describe the uses of different radioactive materials in the home and industry. Explain what is meant by the term ‘half-life’ of a radioactivity material. Describe why half-life is a useful tool when considering how to use radioactive materials. Half-Life – What will we look at next? Half-life is an important consideration when using radiation. In medicine we sometimes inject small amounts of radiation and use a scanner to map its path showing blockages – what might be the best half-life?

Half-Life – What will we look at next? Learning Objectives By the end of this lesson you should... Describe the uses of different radioactive materials in the home and industry. Explain what is meant by the term ‘half-life’ of a radioactivity material. Describe why half-life is a useful tool when considering how to use radioactive materials. Half-Life – What will we look at next? Using the text books research the uses of radioactive materials in the “real world “ Finding out how old something is (dating) Treatment of diseases Tracing the path of something Any others