Hazards & Uses of Radioactive Emissions & of Background Radiation (AQA GCSE Physics): Exam Questions

Figure 1 shows a bottle of radioactive tracer which can be injected into a patient.

Figure 1

Explain the ideal properties of a radioactive source for use in medical diagnosis.. 

A student carried out an investigation to measure the count rate from a radioactive source at different distances from the source.

She used the equipment in Figure 2.

Figure 2

Her results are shown in Table 1 below.

Table 1

The student has corrected her results to take account of background radiation.

What is the value of the background count rate?

Background count rate =  ____________ counts per minute

The radiation source that the student used is not an alpha emitter.

How can you tell from the data in the table?

Plot a graph of corrected count rate against distance for distances between 0.1 m and 1.5 m.

Draw a line of best fit.

An A level student used a Geiger-Muller (GM) tube and counter to measure the level of background radiation in his classroom.

The student set the counter to zero, let it run for one minute, and then wrote down the reading.

This procedure was repeated two more times, the results are shown in Table 2 below.

Each of the three readings is correct.

Why are the readings different?

Calculate the value of background radiation the student should account for in any experiments they carry out.

Name one naturally-occurring source of background radiation.

Name one man-made source of background radiation.

Food irradiation is a process that exposes food to radiation in order to kill any bacteria that may be on the food.

This allows the food to be stored for much longer periods of time without it going rotten, or ripening too much.

Foods which are inside packaging can also be irradiated.

Table 3 shows some information about different radioactive isotopes.

Table 3

Which of these radioactive isotopes would be most suitable for the process of irradiating food? 

Justify your choice.

Some people without a good education in science think that food should not be irradiated.

They are concerned about the safety and the nutritional value of eating irradiated foods.

Suggest one reason why some people may have concerns about the safety of irradiated food.

The scientific communities in several countries, including the UK, Canada, France, Germany and North Korea, have concluded that it is safe to eat irradiated food.

These scientific communities need to be independent of any government influence.

Suggest why.

In restaurants, meals which contain irradiated ingredients must be clearly marked on the menu.

Suggest why people think it is important that they are given this information.

Table 4 gives information about six radioactive isotopes

Table 4

Two isotopes of uranium are given in the table. 

Compare the nuclei of these two isotopes.

A doctor needs to monitor the blood flow through a patient’s kidney.

To do this, they inject a radioactive tracer into the patient, and then monitor the level of radiation in the kidney using a GM detector and counter outside of the patient’s body.

Justify which one of the isotopes in Table 4 would be most suitable as a medical tracer inside the human body.

Justify which of the radioisotopes from Table 4 would be most suitable for monitoring the thickness of aluminium foil.

Watering a plant with a solution containing a radioactive isotope can help scientists to understand the growth processes occurring within it.

Using information from Table 4, suggest why phosphorus-32 would be suitable as a tracer in a growing plant.

A radioactive isotope is used in a medical tracer.

The activity of the tracer is measured over time.

Table 2 shows the activity of the tracer at different times.

Table 2

What is meant by 'half-life' of a radioactive isotope?

Tick (✓) one box.

Determine the half-life of the radioactive isotope used as a medical tracer. Use data from Table 2.

Calculate the activity of the tracer after 20 hours.

Use data from Table 2.

The tracer emits beta radiation.

State one reason why beta radiation is suitable for use as a medical tracer.

Which two of the following statements are correct about beta radiation?

Tick (✓) two boxes.

Explain why the patient is not a danger to other people after the scan. Use data from Table 2.

Define the term half-life.

A doctor uses gamma radiation to produce an image of a person's brain as shown in Figure 1. The doctor injects a solution of technetium-99m, a radioactive isotope, into the patient. A detector outside the patient received gamma radiation to form the image.

Figure 1

Technetium-99m emits gamma rays and has a short half-life.

Explain why isotopes that emit alpha particles or beta particles are not suitable for this use.

Technitium-99m has a half-life of 6 hours. A sample of technitium-99m has an activity of 420 MBq.

Calculate the activity of the technitium-99m sample after 24 hours.

    Activity = ..............................................MBq 

Explain why technicium-99m has a suitable half-life for use as a radioactive tracer.

There are two sources of alpha radiation in some houses:

• Radon gas in the air

• Solid americium in a smoke alarm

Explain why the alpha particles from radon are a greater risk to health than the alpha particles from americium.

Figure 1 shows how the activity of a sample of radon-220 changes with time which is measured in seconds.

Figure 1

Label the axes on the graph.

Use Figure 1 to find a value for the half-life of radon-220.

   Half-life = .................................................... s

Explain why the risk to health from Radon gas is low.

A hospital uses a radioactive isotope to investigate blood flow.

The count rate from a sample is measured using a Geiger–Müller (GM) tube.

The medical physicist measures the background count rate four times.

The results are:

Calculate the mean background count rate.

The teacher places the radioactive sample near the GM tube.

The measured count-rate (including background) is recorded every two hours.

Table 3 shows the results.

Table 3

Determine the half-life of the radioactive isotope.

Show how you used the data in Table 3 and your answer to part (a).

Predict the measured count-rate of the sample after 8 hours.

The isotope emits beta radiation.

Explain why a beta emitter is suitable for investigating blood flow inside the body, but an alpha emitter is not.