Practise Radioactive decay and nuclear radiation. 14 exam-style questions on this subtopic, at up to four difficulty levels, with full mark schemes and a progress tracker. Free, no account needed.
Cover the answers and test yourself. The app has these as flashcards that come back just before you'd forget them.
Complete the sentence. Radioactive decay is a ................ process, so it is not possible to predict when a particular nucleus will decay.
random
What is meant by ionising radiation?
Radiation that knocks electrons out of atoms, turning them into ions.
State the material (or substance) needed to stop alpha particles.
Paper (or skin, or a few cm of air).
A different school, using the same type of source and the same method, gets similar count-rate readings to the teacher's class. Which term describes results that are similar when a different experimenter repeats the method: repeatable or reproducible?
Reproducible.
Sample questions
Written for this site in the style of AQA exam questions. They are not taken from real past papers.
Question 1Easy4 marks
(a) What is an alpha particle made of? Tick (✓) one box.[1]
Two protons and two neutrons
A high-speed electron
Electromagnetic radiation
A single neutron
(b) What is a gamma ray? Tick (✓) one box.[1]
A helium nucleus
A high-speed electron from the nucleus
Electromagnetic radiation from the nucleus
A neutron from the nucleus
(c) Complete the sentence. Radioactive decay is a ................ process, so it is not possible to predict when a particular nucleus will decay.[1]
(d) What is the unit of activity?[1]
Show the answer and mark scheme
(a)Answer: Two protons and two neutrons
(b)Answer: Electromagnetic radiation from the nucleus
(c)Answer: random
random
(d)Answer: Becquerel (Bq)
becquerel (Bq)
Question 2Medium6 marks
(a) What is meant by ionising radiation?[2]
(b) Alpha particles are the most strongly ionising type of nuclear radiation. Explain why alpha particles have the shortest range in air.[2]
(c) Which type of nuclear radiation is the least ionising?[1]
(d) As well as alpha particles, beta particles and gamma rays, an unstable nucleus can emit one other type of nuclear radiation. Name it.[1]
Show the answer and mark scheme
(a)Answer: Radiation that knocks electrons out of atoms, turning them into ions.
radiation that can remove electrons from atoms
turning the atoms into (positive) ions
(b)Answer: They ionise a lot of air molecules along their path, so they lose their energy within a few centimetres.
alpha particles collide with and ionise many air molecules / cause a lot of ionisation along their path
so they lose their energy quickly and are stopped after a few centimetres
(c)Answer: Gamma
gamma (rays)
(d)Answer: A neutron
neutron(s)
Question 3Hard7 marks
A teacher has a sealed radioactive source. It emits one or more types of nuclear radiation. The teacher also has:
a Geiger–Müller tube connected to a counter
a stopwatch
a sheet of paper
a sheet of aluminium 3 mm thick
a sheet of lead 5 cm thick
(a) Describe how the teacher could find out which types of radiation the source emits. Your answer should include how the teacher would use the results.[6]
(b) Explain why the distance between the source and the Geiger–Müller tube must be kept the same throughout the experiment.[1]
Show the answer and mark scheme
(a)Answer: Measure background; then count rate with no absorber, paper, aluminium and lead at a fixed distance and time; subtract background. A drop with paper shows alpha, a further drop with aluminium shows beta, a count above background through aluminium or lead shows gamma.
measure the background count with no source present over a set time (e.g. 5 minutes) and calculate the background count rate
place the source a fixed, short distance (e.g. 2 cm) from the Geiger–Müller tube and measure the count rate with no absorber
place the paper between the source and the tube and measure the count rate again, keeping the distance and counting time the same
repeat with the aluminium sheet and then with the lead sheet
subtract the background count rate from each reading
if the paper reduces the count rate significantly, alpha is emitted
if the aluminium reduces the count rate significantly more than the paper, beta is emitted
if the count rate with the aluminium or the lead is still above background, gamma is emitted
safety: handle the source with tongs, keep it away from the body and return it to its lead box as soon as possible
Marked with levels of response: the full level descriptors are in the app.
(b)Answer: So that any change in count rate is due only to the absorber, not to a change in distance.
the count rate also depends on the distance (air absorbs some radiation), so keeping it the same means any change in count rate is caused only by the absorber