14   8 A teacher demonstrated the decay of protactinium using a Geiger-Müller (GM) tube connected to a data logger. A sealed plastic bottle contains a solvent floating above a liquid containing a uranium salt. Protactinium is produced from the decay of uranium and is present in the solvent as shown. GM tube sealed plastic bottle liquid containing uranium solvent containing protactinium to data logger (a) Deduce whether alpha radiation or beta radiation from the inside of the bottle is detected by the GM tube. 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(b) The data logger output is shown below. 450 400 350 300 250 200 150 100 50 0 10 9 8 7 6 5 4 3 2 1 0 t / s Count rate / s−1 Turn over 15   (i) Determine the half-life of the protactinium. 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Half-life of protactinium = ....................................................... (ii) Explain why the count rate doesn’t reach zero. 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(Total for Question 8 = 8 marks)