1 Radiation and Radioactivity_Answer Structured Questions (<8 marks) (Level 1) 1 (a) (i) radiation (1A) (ii) radiation (1A) (iii) radiation (1A) (iv) radiation (1A) (b) radiation is used thickness gauges to monitor the thickness of paper or plastic sheets produced in a factory. (1A) 2 , and radiation radiation radiation radiation (3A) Alpha particles carry positive charges. Using Fleming’s left hand rule, it can be predicted that (1A) . Beta particles carry negative charges. Hence, radiation deflects in the opposite direction to radiation. Since a particle is lighter than a particle, radiation shows a larger scale of deflection (1A) . Gamma radiation is unaffected by the magnetic field and it travels straight (1A) . 3 (a) Gamma ( ) radiation source is the most suitable (1A) because and radiation cannot penetrate a lead sheet (1A) . (b) The amount of radiation passed through the lead sheet varies with the thickness of the sheet (1A) . The detector monitors the amount of radiation received and sends feedback signals to another part that controls the thickness of the lead sheet produced (1A) .
2 4 (a) and radiations are emitted from the source (1A) . The recorded count rate drops significantly after a piece of paper is inserted. This indicates that radiation is emitted from the source (1A) . The recorded count rate also drops significantly after a piece of 25 mm aluminium is inserted. This indicates that radiation is emitted from the source (1A) . The recorded count rate only varies slightly after a piece of 25 mm lead is inserted. This indicates that no radiation is emitted from the source (1A) . (b) Using a cloud chamber can identify the types of radiation emitted from the source (1A) . radiation produces thick and straight tracks in a cloud chamber. The appearance of right-angled fork tracks also indicates the presence of particles (1A) . radiation produces thin and irregular tracks in a cloud chamber while radiation produces scattered tracks which are almost unobservable (1A) . (or any reasonable answers) 5 (a) Ions are produced by the sources between the two conducting plates (1A) . They complete the circuit so that current passes through the milliammeter (1A) . (b) radiation is emitted (1A) . It is because radiation has the strongest ionizing power among the three kinds of radiation and more ion pairs can be produced (1A) . (c) I do not agree (1A) . It is because there are few gas molecules available to be ionized in an evacuated chamber. The milliammeter is not able to measure such a small size of current (1A) . 6 (a) As particles will be stopped by a sheet of 2 mm-thick paper and they cannot reach the photographic film, radiation cannot be detected by the badge. (1A) (b) If the badge is exposed to radiation, region B of the developed film will be blackened (1A) . It is because particles can pass through a sheet of paper but they will be stopped by a 5 mm-thick aluminium sheet. Therefore, radiation can only reach region B of the photographic film (1A) .
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