Long Questions_ch18 - cfw_<part=E><chapter=18><type=LQ(over_9_marks)><marks=14><section=core><s kill=drilling><id=101> 183101 In an experiment

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1ccd7d9da2d1f76d0bf27b340fb5bd1c9579b1d5.doc {{<part=E><chapter=18><type=LQ_(over_9_marks)><marks=14><section=core><s kill=drilling><id=101>}} 183101 In an experiment distinguishing α and β particles from a radioactive source, an electric field is set up with field direction pointing upwards. The following figure shows the set-up and the paths of α and β particles in the field. (a) What is the function of the narrow opening in the lead block? (1 mark) (b) Which path do α particles take, A or B ? Explain your answer. (3 marks) (c) Now the two types of particle are emitted in a magnetic field. (i)Copy the figure below. Sketch and label the paths of αand β B × × × × × × × × × × × × × × ×
(i) outside the body; (ii) inside the body. Assume that the two sources have the same activity. (6 marks) -- ans -- Solutions Marks (a) It is used to produce a unidirectional narrow beam of particles. 1A (b) α particles take path B . 1A α particles carry positive charges; thus the force acting on them is in the same direction as that of the electric field. 1A 1A (c) (i) (correct path of α ) (correct path of β ) 1A 1A (ii) See the above sketch. ( X bends upwards) (larger curvature) 1A 1A (d) (i) An α source causes less damage than a β source if both of them are outside the body. 1A It is because the penetrating power of α radiation is very weak and only a very little amount of the radiation can enter the body. 1A 1A (ii) An α source cause more damage than a β source if both of them are inside the body. 1A It is because α radiation has much stronger ionizing power; 1A 1ccd7d9da2d1f76d0bf27b340fb5bd1c9579b1d5.doc | 2 × × × × × × × × × × × × × × × X A B
1ccd7d9da2d1f76d0bf27b340fb5bd1c9579b1d5.doc thus it causes more serious damage to the body cells. 1A -- ans end -- {{<part=E><chapter=18><type=LQ_(over_9_marks)><marks=13><section=core><s kill=drilling><id=102>}} 183102 The following experimental set-up is used to investigate the effect of a magnetic field on α , β and γ radiation emitted by a radioactive source. The experiment is carried out in a vacuum and an uniform magnetic field pointing into the page is applied. From the photographic film, only P and Q are exposed to radiation. (a) Copy the above figure. Sketch and label the paths of the α , β and γ radiation emitted from the source.

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