GCSE Questions: Radioactivity
Q1.
(a) Alpha particles (α), beta particles (β) and gamma rays (γ) are types of nuclear radiation.
(i) Which of the three types of radiation is the most strongly ionising?
(1 mark)
Alpha particles 
(ii) What effect does nuclear radiation have on living cells?
(1 mark)
It damages them or changes DNA or kills/destroys them.
OR it causes cancer or causes cell mutations
Do not accept simply 'they ionise cells'
(b) The diagrams show a G-M tube and counter used to measure the radiation emitted from a source. Both diagrams show the reading on the counter one minute after it was switched on.
Explain why the counter readings show that the source is giving out only gamma radiation.
(2 marks)
The count is (roughly) the same. Gamma radiation is not affected by a magnetic field, whereas alpha and beta would be deflected by the magnet, therefore if alpha or beta made up the count in the first instance the presence of the magnet would make the count would go down significantly.
(c) The box gives information about the radioactive isotope technetium-99. What is meant by the term half-life?
(1 mark)
It is the time taken for number of radioactive nuclei in the sample to halve.
Or the time taken for count rate to fall to half its initial value.
(d) To study the blood flow in a patient's lungs, a doctor injects a small quantity of a technetium-99 compound into the patient. The radiation emitted by the technetium-99 atoms is detected outside the patient's body. Explain why a doctor would not use a radioactive isotope with a very short half-life, such as 2 seconds, as a medical tracer.
(2 marks)
If the half life was very short there would not be enough time to take measurements or observations before level of radiation became insignificant.
(Total 7 marks)
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