Radioactivity and Particles
4 marks · NormalRead these two statements about radioactivity: Statement 1: The activity of a radioactive sample is measured in becquerels (Bq). Statement 2: Gamma radiation is more penetrating than alpha radiation.
Explain what is meant by the unit 'becquerel' (Bq).
Why is gamma radiation more dangerous than alpha radiation outside the body? Give a reason.
A sample has an activity of 500 Bq. How many decays does this represent per second?
State one common way to detect ionising radiation in a laboratory.
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(a) One becquerel means one decay per second.
(b) Gamma radiation is highly penetrating and can pass through the skin and body, so it can damage internal organs.
(c) 500
(d) Using a Geiger-Muller (GM) tube.
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Marking points
B1 (a) · 1 mark · Gives correct definition of becquerel.
B2 (b) · 1 mark · Explains why gamma is more dangerous outside body (penetrating, reaches organs).
A1 (c) · 1 mark · Calculates 500 Bq = 500 decays per second. (follow-through)
B3 (d) · 1 mark · States detection method (GM tube).
Worked solution
(a) One Bq means one radioactive decay occurs per second.
(b) Gamma rays can pass through the skin and deeper into the body, damaging internal tissues, whereas alpha particles cannot penetrate skin.
(c) 500 Bq means 500 decays every second.
(d) A Geiger-Muller tube is a common detector for ionising radiation in the lab.