ATOMS AND RADIOACTIVITY
4 marks · NormalA student investigates the penetration powers of alpha, beta, and gamma radiation using suitable equipment.
Name the device used to detect ionising radiation in such an experiment.
The student places different materials between the source and the detector. Describe what would be observed for:
(i) Alpha radiation with a sheet of paper
(ii) Beta radiation with 5 mm of aluminium
(iii) Gamma radiation with 2 cm of lead
Work this out on paper, then compare with the answer and worked solution below. With a free account you can submit written answers for marking.
Show answer
(a) Geiger–Müller tube (or counter); accept spark counter · must show Geiger–Müller tube/counter
(b(i)) Alpha particles are stopped; no count detected · must show Alpha completely stopped
(b(ii)) Beta is mostly stopped; the count drops nearly to background · must show Beta stopped by aluminium
(b(iii)) Some gamma is still detected; the count decreases but does not reach zero · must show Gamma partially stopped; still detected
Common mistakes: Mixing up which radiation is stopped by which material
Show mark scheme and worked solution
Marking points
B1 (a) · 1 mark · Correctly names Geiger–Müller tube or spark counter.
B2 (b(i)) · 1 mark · Alpha stopped by paper/no count detected.
B3 (b(ii)) · 1 mark · Beta stopped by aluminium/drops to background.
B4 (b(iii)) · 1 mark · Gamma only partially stopped by lead/count decreases, not zero.
Worked solution
a) Geiger–Müller tube (or Geiger counter). b) i. Alpha is stopped by paper; count falls to background. ii. Beta is stopped by 5 mm aluminium; very few or no counts detected. iii. Gamma is only partially stopped by 2 cm lead; count decreases but remains above background.