1. Observing nuclear radiation STARTER ACTIVITY: * List some things we can not see and how we detect them: Invisible things How we detect them Infra-red radiationFace, cheek, thermometer Wind Damage it leaves behind Nuclear radiation Damage it leaves behind ?? Lesson objectives; You will learn: 1. Structure of the atom 2. Why some nuclei decay 3. The 3 types of radiation

2. Observing nuclear radiation 1896 Henri Becquerel: Some photographic paper in a sealed bag was fogged but had the image of a key on it. He deduced that some form of radiation from the uranium rocks had passed through the paper but not the metal key.

3. Observing nuclear radiation Marie Curie, a research worker said these rocks were “Radioactive” * the rocks gave out the radiation all the time * chemicals and heating made no difference She discovered a new radioactive element polonium. She died in middle age of Leukaemia. Q. You can stop a light from giving out light radiation. Is it possible to stop uranium giving out nuclear radiation?

4. Why are some substances radioactive? Some atoms have an unstable nucleus and need to get to a lower energy state. It can become stable by emitting Alpha, Beta or gamma radiation. It “decays”. A decay is a random event -it happens without anything being done to the nucleus.

5. The structure of the atom ELECTRON – negative, mass nearly nothing PROTON – positive, same mass as neutron (“1”) NEUTRON – neutral, same mass as proton (“1”)

6. The structure of the atom 0Electron 01Neutron 11Proton Relative ChargeRelative MassParticle MASS NUMBER = number of protons + number of neutrons SYMBOL PROTON NUMBER = number of protons (obviously)

7. Types of radiation 1) Alpha (  ) – a nucleus decays into a new nucleus and emits an alpha particle (2 protons and 2 neutrons – the nucleus of a helium atom) 2) Beta (  ) – a nucleus decays into a new nucleus by changing a neutron into a proton and electron. The fast moving, high energy electron is called a beta particle. 3) Gamma – after  or  decay surplus energy is sometimes emitted. This is called gamma radiation and has a very high frequency with short wavelength. The nucleus is not changed. Unstable nucleus New nucleus Alpha particle Beta particle Gamma radiation

8. Ionisation When radiation collides with neutral atoms or molecules it alters their structure by knocking off electrons. This will leave behind IONS – this is called IONISING RADIATION.  particle Electron

9. Detecting radiation Gieger-Muller Tube Spark counter Photographic film Cloud chamber What are the different methods?

10. Photographic film 1. What happens to film when radiation is incident upon it? It darkens. 2. Can photographic film tell you the type of radiation incident upon it? No, just the amount of radiation received. 3. What can this be used for? Can be used in radiation badges, that record the exposure of workers to radiation. Different windows detect different types of radiation.

12. Observing nuclear radiation