radiation poisoning is insufficient ionising is insufficient 1 3 b i any one

Radiation poisoning is insufficient ionising is

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radiation poisoning is insufficient ionising is insufficient 1 3 (b) (i) any one from: use tongs to pick up source wear gloves use (lead) shielding minimise time (of exposure) maximise distance (between source and teacher). accept any other sensible and practical suggestion ignore reference to increasing / decreasing the number / thickness of lead sheets 1 (ii) background 1 Page 5 of 44
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(c) (i) curve drawn from point 2,160 do not accept straight lines drawn from dot to dot 1 (ii) (also) increases less radiation passes through is insufficient 1 (iii) 50 accept any value from 40 to 56 inclusive 1 (d) gamma 1 only gamma (radiation) can pass through lead accept alpha and beta cannot pass through lead a general property of gamma radiation is insufficient 1 [8] (a) (average) time taken for the amount / number of nuclei / atoms (of the isotope in a sample) to halve or time taken for the count rate (from a sample containing the isotope) to fall to half accept (radio)activity for count rate 1 4 (b) 60 ±3 (days) 1 indication on graph how value was obtained 1 (c) (i) cobalt(-60) 1 gamma not deflected by a magnetic field or gamma have no charge dependent on first marking point accept (only) emits gamma gamma has no mass is insufficient do not accept any reference to half-life 1 (ii) strontium(-90) 1 Page 6 of 44
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any two from: only has beta alpha would be absorbed gamma unaffected beta penetration / absorption depends on thickness of paper if thorium(-232) or radium(-226) given, max 2 marks can be awarded 2 (iii) cobalt(-60) 1 shortest half-life accept half-life is 5 years dependent on first marking point 1 so activity / count rate will decrease quickest 1 (iv) americium(-241) / cobalt(-60) / radium(-226) 1 gamma emitter 1 (only gamma) can penetrate lead (of this box) do not allow lead fully absorbs gamma 1 [14] (a) (i) nuclear reactor 1 5 star 1 (ii) nuclei are joined (not split) accept converse in reference to nuclear fission do not accept atoms are joined 1 Page 7 of 44
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(b) (i) any four from: neutron (neutron) absorbed by U (nucleus) ignore atom do not accept reacts do not accept added to forms a larger nucleus (this larger nucleus is) unstable (larger nucleus) splits into two (smaller) nuclei / into Ba and Kr releasing three neutrons and energy accept fast-moving for energy 4 (ii) 56 (Ba) 1 57 (La) if proton number of Ba is incorrect allow 1 mark if that of La is 1 greater 1 accept e for β scores 3 marks 1 [10] (a) (i) 18 1 6 (ii) the count rate for the source 1 (iii) the alpha radiation would not cover such a distance 1 (iv) plots correct to within ½ small square allow 1 mark for 4 correct points plotted 2 correct curve through points as judged by eye 1 (v) two attempts at finding ‘half-distance’ using the table 20 to 10 cpm d = 0.4 m 125 to 56 cpm d = 0.2 m 31 to 14 cpm d = 0.4 m allow 1 mark for one attempted comparison 2 Page 8 of 44
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obeyed or not obeyed dependent on previous two marks 1 (b) (i) there is no effect on the count rate in experiment 1 because the field is parallel or beta particles are not deflected or there is no force 1
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  • Alpha, Ionizing radiation, accept α

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