b The ammeter reading decreases gradually and drops to zero when the source is

B the ammeter reading decreases gradually and drops

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(b) The ammeter reading decreases gradually and drops to zero when the source is a few centimetres away from the plates. 1A The range of radiation in the air is about several centimetres. 1A No ion is formed between the plates when the plates are out of the range of radiation, and hence no current flows. 1A 13 Solutions Marks (a) Nuclear radiation can damage living cells. 1A Long-term exposure to nuclear radiation may cause cancer. 1A (Or other reasonable answers) (b) Stay at a longer distance from the sources. 1A Shield the sources with thick lead. 1A (Or other reasonable answers) 14 Solutions Marks (a) This is because radiation from a radioactive source is emitted at random. 1A (b) As the count rates drop significantly to background level when a sheet of paper is inserted, 1A this shows that the radioactive source emit radiaton only. 1A (c) Any two of the following: 2 1A Store and transport all sources in suitable lead containers. Handle the source with forceps or special lifting tools. Label the storage place with warning signs. (Or other reasonable answers)
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