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The Curie family

The Curie family. Radioactive. Some substances give out radiation all the time – these are radioactive. They do not need encouraging or triggering in any way. A new substance may form The process is called radioactive decay and emission. Radioactive decay. The decay process is random

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The Curie family

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  1. The Curie family

  2. Radioactive • Some substances give out radiation all the time – these are radioactive. They do not need encouraging or triggering in any way. • A new substance may form • The process is called radioactive decay and emission

  3. Radioactive decay • The decay process is random • No one can predict when 1 nucleus decays • The emission is spontaneous • It is possible to make a statistical prediction.

  4. Geiger counter

  5. Types of radiation There are three types of radiation • Alpha -α • Beta -β • Gamma -γ • Radioactive rays cannot be seen • They are detected using a Geiger counter

  6. Absorption of radiation γ β 2-10 cm lead 2-3 metres concrete α Thin paper 2-3mm metal

  7. Absorption of radiation – not to be copied!!

  8. Absorption of radiation • Alpha – α – absorbed by 2-3 cm air and thin paper • Beta – β – can penetrate paper absorbed by a few mm of metal • Gamma – γ – very penetrating absorbed by many cm of lead and metres of concrete

  9. Monitoring the thickness of materials An increase in thickness reduces the number of betas passing through the paper.

  10. Background radiation

  11. Background radiation

  12. Radioactivity can be dangerous

  13. The effect of radiation- Ionisation • The atom is ionised by the radiation • Electrons are removed • Ions are formed

  14. Damaging cells • Ionised living cells may cause cancer • Higher dose of radiation – morerisk

  15. Damaging cells Radiation damages the DNA responsible for the reproduction of cells

  16. Killing cells Cells can be killed using radiation

  17. Alpha Beta Gamma Inside and ouside Radiation will ionise atoms in living cells – this can damage them and cause cancer or leukaemia. OUTSIDE the body  and  are more dangerous as  radiation is blocked by the skin. INSIDE the body an  source causes the most damage because it is the most ionising.

  18. The danger of radiation sources - outside of the body - 1 Betas and gammas are the most dangerous • they can penetrate and reach the cells of organs • They are absorbed and ionise the cells • This can cause cancer Alphas are the least dangerous

  19. The danger of radiation sources - outside of the body - 2 Alphas are the least dangerous They cannot penetrate the air and reach living cells

  20. The danger of radiation sources – inside the body • Alpha radiation is the most dangerous as it is strongly absorbed and ionises cells • Betas and gammas are not strongly absorbed and cause less ionisation damage

  21. Radioactivity can be very useful

  22. Gamma radiation in medicine - therapy Gamma rays used to kill cancer cells and destroy tumours.

  23. Killing cells using gamma radiation Gamma rays are used to kill cancer cells and bacteria

  24. Killing cells using gamma radiation Gamma rays are used to kill bacteria

  25. Gamma radiation in medicine - diagnosis Gamma cameras used to detect tumours - diagnosis

  26. Gamma camera image • The patient is injected with a source of gamma radiation • This is absorbed by some body tissue. • It is emitted and detected by the gamma camera

  27. Nuclear bomb The gamma rays they emit can travel long distances without absorption

  28. Radiation burn This has been caused by long exposure to gamma rays

  29. The radiation badge A B C

  30. Gamma source Tracers Tracers – a tracer is a small amount of radioactive material used to detect things, e.g. a leak in a pipe: The radiation from the radioactive source is picked up above the ground, enabling the leak in the pipe to be detected. Tracers can also be used to develop better plant fertilisers and in medicine to detect tumours:

  31. Alpha radiation - 1 • = 2 protons + 2 neutrons • +ve • Heavy • Strong ionisers • Penetrate 5cm α 4 2

  32. Alpha radiation - 2 X Y + α

  33. Alpha radiation - 3 Alpha decay

  34. Gamma radiation -1 • = transverse waves • No charge • No mass • Weak ioniser • Penetrates air, aluminium, • thin lead γ 0 0

  35. Gamma radiation -2 X Y + γ

  36. Gamma radiation - 3 Gamma decay

  37. Beta radiation -1 • = electron from the nucleus • -ve • Light • Medium ionisers • Penetrate 30cm air, paper, thin aluminium β 0 -1

  38. Beta radiation -2 X Y + β

  39. Beta radiation - 3 Beta decay

  40. Radioactive decay ½ life 16 8 4 2 0 8 12 14 +α,β,γ X Y

  41. R.A.Decay tablehalf life = 3 days

  42. R.A.Decay tablehalf life = 12 years

  43. R.A.Decay tablehalf life = 4.5 years

  44. The R.A.decay graph Half life = 6.8days

  45. The R.A.decay graph

  46. Half life – of radioactive Phosphorus P S + β

  47. Half life – of radioactive Carbon 14 C N + β

  48. Radioactive decay - 1 • A radioactive nucleus emits radiation – an alpha, beta or gamma • A new nucleus is formed • One element turns into another element • The radioactivity decreases – less radiation is emitted

  49. Radioactive decay - 2 • The decay process is random • No one can predict when 1 nucleus decays • The emission is spontaneous • It is possible to make a statistical prediction.

  50. Radioactive decay – half life • The time it takes for half the R.A. nuclei to decay is called the half life. • The time taken for the radioactivity to half is the same. • Different R.A. substances have different half-lives.

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