1. Radioactivity P1b 6.1-2 Observing Alpha, Beta and Gamma radiation

2. Learning objectives Understand why some elements are radioactive, and how this can be detected Understand why some elements are radioactive, and how this can be detected Understand the different properties of different radiations Understand the different properties of different radiations Know the dangers of radiation Know the dangers of radiation

3. What’s this?...It’s radioactivity! Henri Becquerel Henri Becquerel Uranium Uranium Marie Curie Marie Curie Leukaemia Leukaemia

4. What stops radiation? Ernest Rutherford – tested different materials Ernest Rutherford – tested different materials Alpha radiation (α) – stopped by paper Alpha radiation (α) – stopped by paper Beta radiation (β) – went straight through Beta radiation (β) – went straight through Later discovered, Gamma radiation (γ) Later discovered, Gamma radiation (γ)

5. Radioactive puzzle Why are some things radioactive? Why are some things radioactive? Un-stable nucleus emits particles - decay Un-stable nucleus emits particles - decay

6. Testing for radiation Different type travel different distances in air Different type travel different distances in air Detecting in air – move away from source Detecting in air – move away from source

7. Gamma radiation has no mass or charge so it is not deflected. Beta radiation has a –ve charge and a small mass so is strongly deflected Alpha radiation has a +2 charge but has a greater mass so is only weakly deflected. Effect of a magnetic or electric field on radiation depends upon the nature of the radiation. Effects of a field on radiation

8. Alpha Beta Gamma Negatively charged Helium nuclei High energy electron Electromagnetic radiation Stopped by paper or skin Reduced by lead Stopped by aluminium Match the radiation

9. High exposure kills cells Low exposure causes cancer Higher the exposure = higher risk Alpha = most ionising radiation, gamma = least. Ionising radiation can be used to kill cancer cells Radiation can ionise cells causing cellular damage Ionising radiation

10. Learning outcomes Why are some elements are radioactive? Why are some elements are radioactive? How do properties of alpha, beta and gamma radiations differ? How do properties of alpha, beta and gamma radiations differ? What are the dangers of radiation? What are the dangers of radiation?