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

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.

Give one naturally-occurring source of background radiation

Give 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? 

Explain the reasons for 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 from 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

Two isotopes of uranium are given in the table. 

How do the nuclei of these two isotopes differ?

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.

Which one of the isotopes in Table 4 would be most suitable as a medical tracer inside the human body?

Explain the reasons for your choice.

Which of the radioisotopes from Table 4 would be most suitable for monitoring the thickness of aluminium foil?

Explain the reasons for your choice.

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, explain why phosphorus-32 would be suitable as a tracer in a growing plant.

A brave student placed a radioactive source in front of a Geiger-Muller detector and measured the count rate every 10 minutes.

The student needs to correct her data for background radiation.

Describe how the student should measure the background radiation and correct the count rate readings.

Give two sources of background radiation

Scientists need to reduce the risks when working with radioactive sources.

Explain why radioactive sources can be dangerous to humans.

Describe sensible precautions scientists can take when working with the kind of radioactive sources used in school science lessons.

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.

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.

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

Figure 1 shows equipment which can be used to investigate the half-life of a radioactive source.

Figure 1

State two sources of background radiation.

Describe the method that should be used to correct for background radiation.

Complete the following sentences about the investigation using variables from the list below:

The independent variable is .................... .

The dependent variable is .................... .

The control variables for the experiment are ...................... , .................... and ...................... .

Suggest the properties this isotope would need in order to be used as a medical tracer.