Radioactive decay & nuclear radiation

This question is about the process of controlled nuclear fission in a nuclear reactor.

In a nuclear reactor, uranium‑235 nuclei are split to produce daughter nuclei and neutrons.

State what else is released in nuclear fission that makes the process useful in a nuclear reactor.

What is the function of the control rods in a nuclear reactor?

What is the function of the moderator in a nuclear reactor?

Many of the daughter nuclei produced in nuclear fission are very radioactive.

These daughter nuclei decay by emitting ionising radiation in a random process.

State what is meant by the term ionising radiation.

State what is meant by the term random process.

The diagram shows some parts of a nuclear reactor.

Explain the role of shielding in a nuclear reactor.

The photograph shows a cloud chamber, used to observe alpha radiation produced by a radioactive source. The radioactive source is inside the cloud chamber, as shown in the photograph.

Describe the structure of an alpha particle.

The source used in the cloud chamber contains the isotope radium-226.

The incomplete nuclear equation shows the decay of radium-226 into an isotope of radon.

Complete the nuclear equation by writing the correct numbers in the boxes.

The tracks in the cloud chamber can be seen through the glass viewing window.

Explain why the radioactive source is not a hazard to the person viewing the cloud chamber.

When radiation is emitted from the source a white line is produced in the cloud chamber. The white line is known as a track.

The diagram shows the tracks produced by the radiation from the source.

The diameter of the cloud chamber is also shown.

Explain the properties of alpha radiation that can be deduced from the length of the tracks.

A protactinium generator is a device that can produce samples of an isotope called protactinium‑234m.

A teacher investigates the activity of protactinium‑234m using the apparatus shown in the photograph.

The teacher uses a radiation detector to detect the radiation emitted from the protactinium‑234m.

Give the name of a suitable radiation detector.

Give two safety precautions to minimise the risk of harm to the teacher from the radiation emitted by the protactinium generator.

Protactinium‑234m decays with a half‑life of 70 seconds.

The initial count rate is 840 counts per second.

Calculate the expected count rate after 140 seconds.

count rate =_........ counts per second

The activity of an isotope is the total amount of radiation emitted each second.

The teacher estimates that only 5% of the total radiation emitted is detected by the radiation detector.

Estimate the activity of the isotope when the count rate is 840 counts per second.

Give the unit.

This question is about gamma radiation.

Which of these statements is correct for gamma radiation?

A student uses a simulation to investigate gamma radiation.

This is the student’s method.

• place a Geiger‑Muller (GM) tube a distance of 6 cm from a source of gamma radiation

• measure the count for a time of 10 seconds

• move the GM tube further away from the source and measure the count again.

The student measures the count three times for each distance.

Give a reason why the student takes repeat readings.

The graph shows the student’s results.

The student claims that the data obeys the formula

count × distance² = constant

Evaluate the student’s claim.

This question is about nuclear decay.

Which of these is the same as a beta particle?

Which of these is the same as an alpha particle?

Complete the nuclear equation for an alpha decay.

This question is about radioactivity.

The nucleus of an atom of carbon has 6 protons and 8 neutrons.

Which row of the table shows the nucleus of an atom that is a different isotope of carbon?

Which type of radiation is a high-energy electron?

A nucleus emits radiation. This causes the mass number to decrease by one. The atomic number stays the same.

Which type of radiation does the nucleus emit?

The nucleus of an isotope of uranium can be represented using this symbol.

The nucleus forms part of a positively charged ion.

How many electrons could be in this ion?

A radioactive isotope has an initial activity of 400 Bq.

The half-life of the isotope is 8 hours.

What is the activity of the isotope after 16 hours?

This question is about radioactive isotopes used for medical imaging.

How many neutrons are in the nucleus of an atom of iodine-131?

Iodine-131 is radioactive and decays with a half-life of 8 days.

State what is meant by the term half-life.

The cross () on the graph shows the initial number of atoms in a sample of iodine-131.

Draw three more crosses () on the graph to show how the number of atoms of iodine-131 in the sample changes during three half-lives.

[iodine-131 half-life = 8 days]

Use a curve of best fit on the graph to estimate the time taken for the number of atoms in the sample to decrease to 5000.

When iodine-131 decays, it emits beta radiation and gamma radiation.

A patient swallows a tablet containing iodine-131. The radiation emitted can be detected outside the body.

State the name of a piece of equipment that can detect the radiation emitted by iodine-131.

Give a reason why gamma radiation is more likely to be detected outside the body than beta radiation.

Technetium-99m is another radioactive isotope.

Iodine-131 and technetium-99m are both used as medical tracers. Medical tracers use radiation detected outside the body to diagnose illnesses.

The table gives information about some of the properties of iodine-131 and technetium-99m when they undergo radioactive decay.

Explain why technetium-99m is likely to be safer than iodine-131 when used as a medical tracer.

This is a question about radioactivity.

Which of these is the unit of activity?

Which of these is the correct description of the term half-life ?

A teacher demonstrates how the activity of a radioactive sample changes with time.

The box gives the names of different pieces of equipment.

Complete the sentences using words from the box.

The teacher measures time with a_........ .

The teacher measures the count rate with a_........ and a counter.

The graph shows the teacher’s results.

Draw a circle around the anomalous result.

Use the graph to determine the half-life of the radioactive sample.

Give a reason why the teacher should not expect the data points to lie exactly on the curve of best fit.

Protactinium is an element with several different radioactive isotopes.

Protactinium‑234 has a half‑life of 6.7 hours.

A sample of protactinium‑234 has an initial activity of 800 units.

Give a suitable unit for activity.

On the axes below, sketch a graph for the decay of the sample of protactinium‑234 during its first three half‑lives.

When protactinium‑234 undergoes beta (β^–) decay it becomes uranium‑234.

The incomplete nuclear equation shows this process.

Complete the nuclear equation to show the beta decay of protactinium‑234.

Write your answers in the dashed boxes.

A student suggests an experiment to determine the type of radiation emitted by a different isotope of protactinium, protactinium‑231.

This is the suggested method.

Step 1 connect a suitable radiation detector to a radiation counter

Step 2 place a source of protactinium‑231 at a fixed distance of 3 cm from the radiation detector

Step 3 record the count of detected radiation for a time of one minute

Step 4 place a sheet of paper between the source and detector

Step 5 record the count of detected radiation for a time of one minute

Step 6 repeat Steps 4 and 5 using a sheet of aluminium and then a sheet of lead instead of the sheet of paper

The table shows the results of the investigation when it is done by a teacher.

Which of these is the dependent variable in the investigation?

The student’s method does not allow for background radiation.

Describe how the student’s method should be modified to allow for background radiation.

Describe how the student’s method could be modified to improve the reliability of the results.

Evaluate the data from the experiment to conclude the type of radiation emitted by protactinium‑231.

A teacher investigates the count rate detected from a radioactive source.

State one source of background radiation.

Describe how the teacher could measure the count rate from a radioactive source and correct the count rate for background radiation.

The teacher places a piece of lead sheet between the radioactive source and a radiation detector.

The teacher determines the corrected count rate from the radioactive source three times and calculates the mean.

They repeat this process using different thicknesses of lead sheet.

The table shows their results.

Calculate the mean count rate when the thickness of lead is 6.0 mm.

Plot a graph of mean count rate against thickness of lead.

Draw the curve of best fit.

When there is not a sheet of lead between the radioactive source and the radiation detector, the mean count rate is 484 Bq.

Use the graph to determine the thickness of lead needed to reduce the mean count rate by 25%.

The radioactive source emits only one type of radiation.

Explain which type of radiation this radioactive source emits.

A teacher demonstrates the penetrating ability of alpha, beta and gamma radiation from some radioactive sources.

State a precaution the teacher should take to make sure they are working safely with the radioactive sources.

State the name of a detector the teacher could use to detect the radiation from each source.

Draw crosses () in the table to show which type of radiation cannot penetrate each material in the table.

An alpha particle of mass 6.610^–27kg travelling at a speed of 2.110⁷m/s hits a sheet of paper.

Calculate the kinetic energy (KE) of the alpha particle.

State the work done on the alpha particle when its speed is reduced to 0 m/s by the sheet of paper.

State which energy store of the paper increases when the alpha particle is stopped.

Which statement describes the term atomic number for a nucleus?

Which statement describes the term mass number for a nucleus?

Which statement describes the term isotopes ?

of protons

of electrons

of protons

of neutrons

An atom contains 8 protons, 8 neutrons and 8 electrons.

Which of these would result in a negatively charged ion of the same element?

It is not possible to predict exactly when a radioactive nucleus will decay.

Which feature of radioactive decay best explains this observation?

Which of these is the correct unit for measuring the activity of a radioactive sample?

A material called granite is used as a work surface in a kitchen.

Granite is formed naturally and contains radioactive isotopes.

The granite work surface contributes to the background radiation in the kitchen.

Give another naturally occurring source of background radiation.

Granite contains the isotope thorium‑232 (²³²₉₀Th).

Thorium‑232 decays by a sequence of alpha decays and beta decays to form radon‑220 (²²⁰₈₆Rn).

State two differences between alpha radiation and beta radiation.

The incomplete nuclear decay equation summarises the decay sequence of thorium-232 into radon‑220.

Calculate the number of alpha particles and the number of beta particles emitted in this decay sequence.

Thorium‑232 is a solid and remains in the work surface.

Radon‑220 is a gas and is emitted from the work surface.

Thorium‑232 and radon‑220 both emit alpha radiation.

Discuss the hazards due to the granite work surface when a person is working in the kitchen.

Refer to contamination and irradiation in your answer.

Bismuth‑207 is a gamma emitter and is represented by the symbol

How many neutrons are in the nucleus of an atom of bismuth‑207?

Which of these gives the best description of gamma radiation?

A technician uses this method to investigate the penetration power of gamma radiation.

• place a gamma emitting source at a fixed distance from a radiation detector

• measure the count using the detector, for a period of one minute

• place a thin sheet of lead between the source and the detector

• measure the new count using the detector, for a period of one minute

• increase the number of lead sheets between the source and detector and repeat this process

The table gives some of the variables from the technician’s method.

Complete the table by placing a tick () in each row to show whether each variable is an independent, a dependent or a control variable.

A teacher uses a radioactive source containing atoms of the isotope radium-226.

Give a safety precaution that would reduce the teacher’s exposure to radiation when working with the radioactive source.

Radium-226 can be represented using the symbol

How many neutrons are in the nucleus of an atom of radium-226?

The teacher investigates the type of radiation emitted from the radioactive source.

Give the name of a piece of apparatus that detects ionising radiation.

The teacher finds that the radiation emitted from the radioactive source is not detected when the detector is more than 5 cm away from the source.

State the type of radiation emitted by the radioactive source.

The number of radium-226 atoms in the source decreases over time, with a half-life of 1600 years.

State what is meant by the term half-life.

The radioactive source contains 2.66 × 10²¹ atoms of radium-226.

Approximately how many atoms of radium-226 will remain in the source after 800 years?

This question is about a nuclear fission chain reaction.

Uranium-235 is an isotope of uranium that can undergo nuclear fission.

The table gives some statements about this fission process.

Add ticks (✓) to the table to show which statements are correct.

State which product of nuclear fission causes the next uranium-235 nucleus to split in the chain reaction.

Uranium-235 is radioactive and emits alpha radiation.

Which of these statements describes alpha radiation?

Some of the products of nuclear fission are radioactive because their nuclei have too many neutrons.

These nuclei become more stable when a neutron changes into a proton.

State which type of radiation is emitted by radioactive nuclei with too many neutrons.

Technetium-98 and technetium-99 are isotopes of the element technetium.

Describe the difference between the nuclei of technetium-98 and technetium-99

Technetium-99 is formed when the element molybdenum-99 decays.

Complete the nuclear equation for the decay of molybdenum into technetium-99

Describe an experiment that a scientist could use to demonstrate that the emission from technetium-99 is gamma radiation.

Include details of a safety precaution in your answer.

A scientist measures the count rate at different distances from the technetium source.

The graph shows how the count rate changes with distance from the technetium source.

The scientist suggests that the relationship between the count rate and distance is (distance)² × count rate constant

Use data from the graph to determine whether these results support this relationship.

A teacher investigates the penetrating ability of the gamma rays from a gamma source.

This is the teacher’s method.

• place the gamma source at a distance of 25 cm from a radiation detector

• place a 1 cm thick absorbing material between the source and the detector

• measure the radiation count from the source for a time period of 3 s

• calculate the count rate in counts per second

• repeat the measurement two more times

The teacher repeats this method for different absorbing materials.

Name a suitable radiation detector that the teacher could use.

State the independent variable in the teacher’s investigation.

Explain why every absorbing material used in the investigation has a thickness of 1 cm.

Suggest one improvement the teacher could make to this method.

The table shows the teacher’s results for seven different absorbing materials.

On the grid, plot a bar chart of the mean count rate for each absorbing material.

Why is a bar chart the correct way to display the results?

A student concludes that plastic is the best absorber of gamma radiation because plastic gives the largest mean count rate.

Evaluate the student’s conclusion.

The photograph shows a glass plate made from uranium glass.

Uranium oxide is used to give the glass a green colour.

State what information the numbers 92 and 238 give about the nucleus of this isotope of uranium.

Uranium‑238 decays by alpha emission.

Describe how the nucleus of a uranium‑238 atom changes as a result of alpha emission.

The table gives some information about the uranium glass plate.

Calculate the number of uranium‑238 atoms in the plate.

Uranium‑238 is an alpha emitter and has a half‑life of 4.5 billion years.

Explain why it is safe to eat food from the uranium glass plate.

The radiation kills bacteria on the fruit. 9

This is a question about alpha particles.

Describe the nature of an alpha particle.

The diagram shows the path of an alpha particle as it passes close to a nucleus.

Draw an arrow from point X to show the force on the alpha particle due to the nucleus.

Label this force Y.

Draw an arrow to show the force on the nucleus due to the alpha particle.

Label this force Z.

Explain how the path of the alpha particle shows whether the nucleus is positive, negative or neutral.

The alpha particle experiences a resultant force of 3.6 N and has a mass of 6.610^–27kg.

Calculate the acceleration of the alpha particle.