An alpha particle is a helium nucleus and alpha radiation is stopped by paper or a few centimetres of air, so this Year 11 sheet opens with the alpha particle and its stopping power. Half-life is the time for half the nuclei to decay, measured in becquerels.
Key Takeaways
An alpha particle is a helium nucleus (Q1).
Alpha radiation is stopped by paper or a few centimetres of air (Q2).
Q5 records the definition of half-life.
Section A: Multiple Choice Questions (1 Mark Each)
Choose the correct option for each question.
1.An alpha particle is the same as which of the following?
(a) a helium nucleus(b) a hydrogen nucleus(c) a fast electron(d) a gamma ray
2.Which radiation is stopped by a few centimetres of air or a sheet of paper?
(a) alpha(b) beta(c) gamma(d) all three types
3.A beta particle is which of the following?
(a) a fast-moving electron(b) a helium nucleus(c) a photon(d) a proton
4.Gamma radiation is which of the following?
(a) a high-energy electromagnetic wave(b) a stream of electrons(c) a helium nucleus(d) a beam of neutrons
5.The half-life of a radioactive isotope is defined as which of the following?
(a) the time taken for half the nuclei in a sample to decay(b) the time taken for all the nuclei to decay(c) the time taken for the activity to double(d) the time taken for half the mass to disappear
6.What is the unit of activity of a radioactive source?
(a) becquerel(b) hertz(c) joule(d) coulomb
Section B: Short Answer Type Questions (2 Marks Each)
Show all steps clearly.
7.Describe the nature of alpha radiation.
8.Describe the nature of beta radiation.
9.Describe the nature of gamma radiation.
10.Define half-life.
11.Define the activity of a radioactive source.
12.Give one natural source of background radiation.
13.Give one medical use of radioactivity.
14.State three ways to reduce a person's exposure to radiation.
Section C: Numericals & Word Problems (3 Marks Each)
Apply the concepts to solve the problems. Show all working.
15.A radioactive sample has a half-life of 8 days. If 80 g is present initially, calculate how much remains after 24 days.
16.A sample has a half-life of 6 hours. If 20 g is present initially, calculate how much remains after 18 hours.
17.The count rate from a source falls from 1600 counts per minute to 100 counts per minute. Calculate the number of half-lives that have passed.
18.A sample has a half-life of 5 days. Its activity falls from 480 Bq to 60 Bq. Calculate the time this takes.
19.A source has an activity of 2000 Bq and a half-life of 2 hours. Calculate its activity after 6 hours.
20.A sample has a half-life of 3 hours. After 9 hours, 8 g remains. Calculate the initial mass of the sample.
Answer Key
1. a) a helium nucleus
2. a) alpha
3. a) a fast-moving electron
4. a) a high-energy electromagnetic wave
5. a) the time taken for half the nuclei in a sample to decay
6. a) becquerel
7. Refer to solution guide.
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20. Refer to solution guide.
End of Worksheet
People Also Ask
What is an alpha particle?
A helium nucleus, option (a) in this worksheet (Q1).
Which radiation does paper stop?
Alpha, option (a) in this worksheet (Q2).
What is half-life?
The time taken for half the nuclei in a sample to decay, option (a) in this worksheet (Q5).
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