Background radiation

A teacher investigates a sample of radioactive material.

The graph shows their results.

On the graph, give the unit for activity.

Describe what is meant by the term background radiation.

Describe what is meant by the term half‑life.

Use the graph to determine the half‑life of this radioactive sample.

half‑life =_........ minutes

The teacher suggests that this formula shows the relationship between activity and time taken.

activitytime taken = constant

Use data from the graph to determine if this relationship is correct.

This question is about using carbon dating to find the age of pieces of wood.

The equation shows how carbon-14 forms in the atmosphere.

State the name of particle X.

Carbon-14 decays by beta decay.

State what happens to the number of protons and the number of neutrons in a carbon-14 nucleus when it decays.

A scientist determines how the percentage of carbon-14 remaining in a sample of wood changes with time.

The table shows the scientist’s data.

Plot the scientist’s data on the grid.

Draw the curve of best fit.

Use the graph to determine the age of a sample of wood that has 36% of its carbon-14 remaining.

Carbon-14 dating is inaccurate for samples of wood produced after 1950.

This is because the concentration of carbon-14 in the atmosphere greatly increased due to nuclear weapons testing.

A tree absorbs carbon-14 during its lifetime.

A student suggests that trees grown after 1950 are contaminated with carbon-14.

Give a reason why the student’s suggestion is correct.

Explain how nuclear weapons testing affects the determination of the age of a sample of wood produced after 1950.

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 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.

Radon is a radioactive gas that contributes to background radiation.

Describe what is meant by the term background radiation.

The graph shows the activity of a sample of radon‑222.

State what is meant by the term half‑life.

Use the graph to determine the half‑life of radon‑222.

Radon‑222 is formed by multiple alpha decays of uranium‑234.

Complete the nuclear equation by giving the missing information.

Radon‑222 also emits alpha radiation.

Explain the hazard to humans of breathing in air contaminated with radon‑222.

A scientist wants to determine the half-life of a radioactive isotope.

The scientist measures the count rate from the radioactive isotope.

State how the scientist should correct the count rate for background radiation.

The graph shows how the activity of the radioactive isotope varies with time.

Explain what is meant by the term half-life.

Use the graph to determine the half-life of this isotope.

half-life =_........ minutes

An aircraft travels along a runway.

The aircraft starts from rest and has a constant acceleration of 4.1 m/s².

Calculate the distance required to reach take‑off speed of 75 m/s.

The aircraft takes off and reaches its maximum height above the ground.

At maximum height, the background radiation count rate is higher than on the ground.

Explain what is meant by background radiation.

Suggest why there is a limit to the number of hours that an airline pilot can fly at maximum height.