A beta gauge is calibrated when a sheet of the correct thickness gives 500 counts per minute, including a background count rate of 20 counts per minute. Much later, the source activity has halved. The sheet, detector and background are unchanged. What reading should now be used for the correct thickness?
260260260 counts per minute
250250250 counts per minute
270270270 counts per minute
240240240 counts per minute
97 exam-style questions on Edexcel GCSE Physics 6.5 Uses and dangers of radioactivity, covering 6.5.1 Uses of radioactivity, 6.5.2 Dangers of ionising radiation and precautions, 6.5.3 Half-life and radiation dangers, 6.5.4 Safety precautions for radiation exposure, and 6.5.5 Contamination and irradiation. Each one has a worked solution and a mark scheme showing where the marks go.