A radiation detector is set up in a laboratory to measure background radiation when no radioactive sources are present.
On five separate occasions, the detector is switched on for 1.0 minute1.0\text{ minute}1.0 minute and the background count is recorded. The counts obtained are:
16,20,18,17,19 16, \quad 20, \quad 18, \quad 17, \quad 19 16,20,18,17,19(i) Calculate the average background count rate in counts per minute.
(ii) State why these background readings are not all identical.
(iii) Suggest one natural source of this background radiation.
A sample containing a single radioactive isotope is then brought into the laboratory and placed near the detector. The detector is switched on, and after 1.0 minute1.0\text{ minute}1.0 minute, a total count of 306306306 is recorded.
The half-life of this isotope is 12 hours12\text{ hours}12 hours.
The sample is left in place and the measurement is repeated after 36 hours36\text{ hours}36 hours for another 1.0 minute1.0\text{ minute}1.0 minute interval.
Predict the reading for the total count that will be obtained on this occasion.
144 exam-style questions on CIE IGCSE Physics 5.2.4a Half-life. Each one has a worked solution and a mark scheme showing where the marks go.