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Radiation True or False? 1.You are being bombarded with radiation right now. 2.You are giving off radiation right now 3.Your breakfast was irradiated with.

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Presentation on theme: "Radiation True or False? 1.You are being bombarded with radiation right now. 2.You are giving off radiation right now 3.Your breakfast was irradiated with."— Presentation transcript:

1 Radiation True or False? 1.You are being bombarded with radiation right now. 2.You are giving off radiation right now 3.Your breakfast was irradiated with deadly radiation 4.You can see radioactivity 5.You can feel radioactivity 6.Radioactive substances are only harmful if you touch them 7.If you are irradiated then you become radioactive 8.Radioactivity is not very useful 9.We completely understand what causes radioactivity 10.Do you know the three types of radioactivity. Write them down.. True True ?? False ?

2 PM S5 K1: Distinguish between stable and radioactive isotopes and describe the conditions under which the nucleus is unstable.

3 Alpha radiation - Helium nuclei Description: 2 neutrons, 2 protons (helium nuclei) Electric Charge: +2 Relative Atomic Mass: 4 Penetration power: Stopped by paper or a few cm of air Ionisation effect: Strongly ionising Effects of Magnetic/Electric Field: Weakly deflected ?

4 Beta radiation - high energy electron Description: High energy electron Electric Charge: Relative Atomic Mass: 1/1860th Penetration power: Stopped by few mm of aluminium Ionisation effect: Weakly ionising Effects of Magnetic/Electric Field: Strongly deflected

5 Gamma radiation - Electromagnetic radiation Description: High energy electromagnetic radiation Electric Charge: 0 Relative Atomic Mass: 0 Penetration power: Reduced by several cms of lead or several metres of concrete Ionisation effect: Very weakly ionising Effects of Magnetic/Electric Field: NO deflection

6 Lets have a look at some radioisotopes. Think about how we may be able to use them!

7 Thin mica Thin aluminium stops BETA Thick lead reduces GAMMA Skin or paper stops ALPHA The penetration power of the three types of radiation.

8 So what exactly does cause this radiation?. First we need to look at the structure of the atom

9 Draw diagrams to represent:

10 How did you go? 6 protons 7 neutrons 6 electrons 6 protons 8 neutrons 8 electrons 6 protons 6 neutrons 6 electrons

11 What do we call these? 6 protons 7 neutrons 6 electrons 6 protons 8 neutrons 8 electrons 6 protons 6 neutrons 6 electrons

12 Atoms of the same element with different numbers of neutrons Isotopes

13 Atoms of the same element with different numbers of neutrons Isotopes Because they have the same number of electrons there is NO difference to their chemical behaviour.

14 There are over 2000 different isotopes that have been discovered so far. Only 279 are stable – they do not emit radiation. The rest are unstable and are called radioisotopes The nuclei rearrange to become more stable. As they do so they emit radiation. But which ones are unstable? Lets have a look at some of these isotopes. Stable and unstable Isotopes

15 So why are some nuclei unstable? Some nuclei are unstable because of the proton to neutron ratio. For light elements, stable nuclei have a proton:neutron ration close to 1:1. For heavy elements the stable nuclei have a proton:neutro ratio close to 1:1.5 Stable and unstable Isotopes

16 p = n

17 Uses of radiation

18 Hydraulic ram detector Thickness Control Mill Electronic instructions to adjust rollers. Beta Source A radioactive source is on one side of the material and a detector on the other. If too much radioactivity is getting through, then the material is too thin and the rollers open up a bit to make the material thicker. If not enough radioactivity is detected then the rollers compress to make the material thinner. This method is used in the manufacture of lots of sheet materials: plastics, paper, sheet steel.

19 Leak detection in pipes The radioactive isotope is injected into the pipe. Then the outside of the pipe is checked with a Geiger-Muller detector, to find areas of high radioactivity. These are the points where the pipe is leaking. This is useful for underground pipes that are hard to get near. The radioactive isotope must be a gamma emitter so that it can be detected through the metal and the earth where the pipe leaks. Alpha and beta rays would be blocked by the metal and the earth. The isotope must have a short half life so the material does not become a long term problem. GM tube

20 Cobalt-60 Sterilisation Gamma rays are used to kill bacteria, mould and insects in ood. Also used to kill bacteria on hospital equipment. This is useful particularly on packaged food or on plastic items which would be damaged by heat sterilisation. It can affect the taste and the vitamin content, but it lengthens the shelf life. Gamma rays are used to kill bacteria, mould and insects in ood. Also used to kill bacteria on hospital equipment. This is useful particularly on packaged food or on plastic items which would be damaged by heat sterilisation. It can affect the taste and the vitamin content, but it lengthens the shelf life. Gamma Source unsterilisedsterilised

21 Sterilisation Cobalt-60 is used as it is a gamma emitter – very penetrating. It has a half life of 5.3 years so the machines can run cheaply without regular maintenance. You dont need external power to produce the gamma rays as you do with x-rays Cobalt-60 is held in a chemically inert form in a sealed container. When the cobalt-60 is exhausted it can easily be replaced. Cobalt-60 is used as it is a gamma emitter – very penetrating. It has a half life of 5.3 years so the machines can run cheaply without regular maintenance. You dont need external power to produce the gamma rays as you do with x-rays Cobalt-60 is held in a chemically inert form in a sealed container. When the cobalt-60 is exhausted it can easily be replaced. Gamma Source unsterilisedsterilised

22 Radioactive half-life The average time taken for half of the substance to decay is called the radioactive half-life.

23 Radioactive half-life What is the half life of Carbon-15?

24 PM S5 K5 – Identify one use of a named radioisotope: in industry In medicine PM S5 K6 – Describe the way in which the above named industrial and medical isotopes are used and explain their use in terms of their chemical properties. (This is your homework – ask for a handout! Include something about half life in your answers.) Start by reading p Cobalt-60 and Technetium 99 are easy to research but it is entirely up to you.

25 Think about this! If the exposure is high, it can kill the cell. If the exposure is lower it can cause cancer. The higher the exposure, the higher the risk of cancer. What happens if radiation is incident upon a living cell? Radiation can ionise cells which causes cellular damage.

26 PM S5 P6 – Use available evidence to analyse benefits and problems with the use of radioactive isotopes in industries and medicine Read p 101 and from what you have learnt today make a list of problems. Read p98 and from what you have learnt today make a list of benefits.

27 PM S5 P6 – Use available evidence to analyse benefits and problems with the use of radioactive isotopes in identified industries and machines. Benefits: Non-invasive diagnostic procedures Treatement of cancers Sensitive monitoring of inductrial processes Sterilisation Non-invasive examination of pipes / aircraft etc. Benefits: Non-invasive diagnostic procedures Treatement of cancers Sensitive monitoring of inductrial processes Sterilisation Non-invasive examination of pipes / aircraft etc. Problems: Tissue damage for people exposed Risk of cancer if exposed Genetic damages to people exposed Hard to dispose of some isotopes (long half-life) Problems: Tissue damage for people exposed Risk of cancer if exposed Genetic damages to people exposed Hard to dispose of some isotopes (long half-life)


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