Radioactivity and Particles
5 marks · NormalA hospital uses a radioactive tracer to detect problems in a patient's kidneys. The tracer contains an isotope that decays by beta emission. The activity of a sample is measured as 3.0 kBq.
State what is meant by the unit becquerel (Bq) and convert the sample's activity to becquerels.
Explain why a beta emitter is often chosen for medical tracers rather than an alpha emitter.
Describe one safety precaution that should be taken when using radioactive tracers in medicine.
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(a) 1 Bq is one decay per second; 3.0 kBq = 3000 Bq
(b) Beta particles are less ionising and less dangerous than alpha inside the body. They can exit the body to be detected, but alpha particles are strongly absorbed and would not be detected easily. Beta causes less damage if retained.
(c) Wear protective gloves, or monitor staff using a film badge, or use the smallest safe dose.
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Marking points
B1 (a) · 1 mark · Correctly defines 'becquerel' as one decay per second.
B2 (a) · 1 mark · Converts 3.0 kBq to 3000 Bq.
B3 (b) · 2 marks · Explains suitable reasons: beta can leave the body/detected, less ionising than alpha, less damage.
B4 (c) · 1 mark · States a valid safety precaution (gloves, film badge, minimum dose, time/distance etc).
Worked solution
a) 1 Bq means one nucleus decays per second. 3.0 kBq = 3.0 × 1000 = 3000 Bq.
b) Beta emitters are chosen because beta can pass through body tissue and be detected outside the body, whereas alpha particles are stopped inside and cannot easily be detected. Also, alpha particles are highly ionising and could damage cells more.
c) Example: Staff should wear protective gloves or use film badges to monitor exposure, or administer the smallest safe amount of tracer.