Define the term background radiation.
State one common natural source of background radiation.
Iodine-131 (53131I^{131}_{53}\text{I}53131I) is a radioactive isotope used in medicine to treat thyroid cancer. It decays by emitting a beta-minus (β−\beta^-β−) particle to form an isotope of xenon (Xe\text{Xe}Xe).
Complete the nuclide equation for this decay by determining the missing nucleon and proton numbers:
53131I⟶ baXe + dcβ ^{131}_{53}\text{I} \longrightarrow \ ^{a}_{b}\text{Xe} \ + \ ^{c}_{d}\beta 53131I⟶ baXe + dcβFind the values of aaa, bbb, ccc, and ddd.
Explain why the beta-emitting source must be placed inside the body, directly at the thyroid, rather than outside the body.
For diagnostic imaging, a different isotope that emits gamma (γ\gammaγ) radiation and has a half-life of 6 hours is injected into the body. The radiation is detected outside the body.
Explain why gamma radiation is suitable for detection outside the body, whereas alpha radiation is not.
Explain why it is beneficial for this diagnostic isotope to have a short half-life of a few hours.
484 exam-style questions on CIE IGCSE Physics 5.2 Radioactivity, covering 5.2.1 Background radiation and measuring count rate, 5.2.2a Alpha, beta and gamma emission, 5.2.2b Deflection and ionising effects of nuclear radiation, 5.2.3a Radioactive decay, 5.2.3b Effects of decay on the nucleus and decay equations, 5.2.4a Half-life, 5.2.4b Choosing isotopes for applications, and 5.2.5 Effects of ionising radiation and safety precautions. Each one has a worked solution and a mark scheme showing where the marks go.