IGCSEScienceEdexcelScience (Double Award) (Modular)Physics Unit 2Exam Questions8. Radioactivity & ParticlesRadioactivity, Uses & Dangers

Radioactivity, Uses & Dangers (Edexcel IGCSE Science (Double Award) (Modular): Physics Unit 2): Exam Questions

Exam code: 4XSD1

2 hours19 questions
Easy
Medium
Hard
1
1 mark

Which of these is measured in becquerel (Bq)? 

  • Activity

  • Frequency

  • Half-life

  • Radiation

Choose your answer

2a
3 marks

Alpha, beta and gamma radiations are described as ionising.

(i) Complete the table to show alpha, beta and gamma radiations in order of increasing ionisation.

[1]

A horizontal arrow labelled least ionising at its left end and most ionising at its right end, above a row of three empty boxes of equal width

(ii) Describe two ways in which these ionising radiations can cause harm.

[2]

How did you do?

2b
3 marks

People who work with ionising radiations need to measure the amount of radiation they are exposed to. For many years, a film badge was used to detect the radiation.

The diagram shows how a film badge is constructed.

A film badge drawn as two overlapping rectangles. The rear rectangle is labelled photographic film. The front rectangle holds nine rounded rectangular windows arranged in three rows of three, shaded in different tones of grey and black, labelled absorber windows in front of film

Complete the table to show if alpha, beta and gamma radiations penetrate each material. Some have been done for you.

Use the words “goes through” or “stopped”.

A table with three columns headed 0.1 cm paper, 0.5 cm aluminium and 0.5 cm lead, and three rows labelled alpha radiation, beta radiation and gamma radiation. Three cells are already filled in: alpha radiation under 0.5 cm lead reads stopped, beta radiation under 0.5 cm aluminium reads stopped, and gamma radiation under 0.1 cm paper reads goes through. The other six cells are empty

How did you do?

3a
2 marks

Radioactivity is used in PET scanners in hospitals.

PET scanners are used to diagnose cancer.

State two precautions that hospital staff might take when working with radioactivity.

How did you do?

3b
2 marks

State two other uses of radioactivity, apart from treatment or diagnosis of cancer.

How did you do?

3c
3 marks

The diagram shows a machine which makes aluminium foil.

The machine uses a radioactive source to measure the thickness of the foil.

Line diagram of a machine that makes aluminium foil. A horizontal line represents the sheet of foil travelling from left to right, shown by two straight arrows pointing right. On the left a pair of labelled rollers, one above and one below the sheet, squeeze it between them; a curved arrow shows the upper roller turning clockwise and another shows the lower roller turning anticlockwise. To the right of the rollers a small labelled radioactive source sits above the sheet and a small rectangular labelled detector sits directly below it, so the foil passes between the two. At the far right the labelled aluminium foil is wound onto a spiral roll, with a curved arrow showing the direction of winding.

The radioactive source emits beta particles. The output from the detector indicates the thickness of the foil.

Complete the following sentences by highlighting the correct answer.

If the aluminium foil gets too thin, the count rate at the detector increases / decreases.

This sends a signal to a computer to push the rollers closer together / further apart.

Beta particles are used because they can / cannot pass through aluminium.

How did you do?

3d
2 marks

Give two reasons why gamma is the most suitable type of radiation for sterilising medical equipment.

How did you do?

4a
1 mark

State the definition of half-life.

How did you do?

4b
3 marks

The half-life of cobalt-60 is 5 years.

The count rate of a sample of cobalt-60 is 100 counts per minute.

(i) How many half-lives are there in 10 years?

[1]

(ii) Calculate the count rate of the cobalt-60 sample after 10 years.

[2]

How did you do?

4c
5 marks

A radioactive isotope can be used as a tracer in a patient’s body. It is monitored by a radiation detector outside the body.

Four possible radioactive isotopes are shown in the table

Radioactive isotope

Type of radiation emitted

Half-life

Radon‐222

Alpha

3.8 days

Iodine‐131

Gamma

8 days

Cobalt‐60

Gamma

5 years

Americium-241

Alpha

470 years

(i) Doctors wear a lead apron when they use radioactive isotopes. Explain why.

[2]

(ii) Which radioactive isotope from the table is best to use as a medical tracer?

Tick (✓) one box.

Radon-222

□

Iodine-131

□

Cobalt-60

□

Americium-241

□

Explain your answer.

[3]

How did you do?

5a
1 mark

Radioactive materials are usually stored in containers lined with metal. This is done to reduce the amount of radiation that escapes, and to protect people nearby.

Which metal is the most effective for this purpose?

  • Aluminium

  • Lead

  • Copper

  • Steel

Choose your answer

5b
1 mark

The risk caused by working with radioactive sources can be minimised by various methods.

Which of the following methods would not minimise this risk?

  • Store the sources in lead-lined boxes

  • Minimise the amount of time spent handling the sources

  • Keep the source hot

  • Keep the source as far away as possible, for example, using a pair of tongs

Choose your answer

5c
1 mark

A student carried out an experiment to find the half-life of a radioactive substance.  Their results are shown in the table below.

time (s)

count-rate (counts / s)

0

300

20

200

40

150

60

100

80

75

State the half-life of the substance.

How did you do?

5d
2 marks

State what is meant by the activity of a radioactive sample, and give its unit.

How did you do?

1a
2 marks

There are two sources of alpha radiation in some houses:

  • Radon gas in the air

  • Solid americium in a smoke alarm

The alpha particles from radon are a greater risk to health then the alpha particles from americium.

Explain why.

How did you do?

1b
5 marks

The graph shows how the activity of a sample of radon-220 changes with time.

Graph of activity against time for a sample of radon-220. The vertical axis is labelled activity in, followed by a blank dotted line where the unit is missing, and is scaled from 0 to 800 in steps of 100. The horizontal axis is labelled time in s and is scaled from 0 to 200 in steps of 25. A smooth curve starts at 700 on the vertical axis at time 0, falls steeply at first and then more gradually, passing through about 350 at 55 s and reaching about 60 at 200 s.

(i) Complete the graph by adding the missing unit for activity.

[1]

(ii) Explain what is meant by the term half-life.

[2]

(iii) Use the graph to find a value for the half-life of radon-220.

[2]

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

How did you do?

2a
2 marks

A smoke alarm contains a source of alpha particles and a detector.

The alpha particles reach the detector through a sample of air from the room.

The alarm sounds if there is a sudden drop in the detector reading.

This graph shows changes in the detector reading.

Line graph with detector reading on the vertical axis and time on the horizontal axis, origin labelled 0 and neither axis carrying a numerical scale. The line begins part-way up the vertical axis, well above the time axis, and wobbles slightly up and down as it drifts gently downwards. A downward arrow labelled alarm sounds marks a point about two thirds of the way along, where the line falls steeply to a much lower level. After the drop the line continues to wobble slightly about that lower level to the right-hand edge, still clearly above the time axis.

(i) Why is the detector reading never zero?

[1]

(ii) Why is the detector reading never constant?

[1]

How did you do?

2b
2 marks

Suggest why fewer alpha particles reach the detector if there is a fire.

How did you do?

3a
4 marks

A teacher shows his class how to investigate the half-life of a radioactive source.

Photograph of laboratory apparatus. On the left is a Geiger counter rate meter, a grey hand-held box with a digital display reading 639 and a row of buttons labelled MODE, START, STOP, SOUND and ON. A cable runs from the top of the meter to a black GM detector on the right, which has a short cylindrical tube pointing to the left. Standing between them is an upright cylindrical container with a metal cap. Two labels with leader lines read radioactive source, pointing to the cylindrical container, and GM detector, pointing to the black box.

The readings from the counter need to be corrected for background radiation.

(i) State one source of background radiation.

[1]

(ii) Describe the method the teacher should use to correct for background radiation.

[3]

How did you do?

3b
6 marks

Every half a minute, the teacher records the count rate. He corrects for background radiation and produces this results table.

A results table with two columns. The left column is headed Time in minutes and the right column is headed Corrected count rate in Bq. The ten rows of data are: 0 and 49, 0.5 and 30, 1.0 and 24, 1.5 and 18, 2.0 and 15, 2.5 and 11, 3.0 and 10, 3.5 and 9, 4.0 and 5, 4.5 and 6.

(i) Draw a graph of corrected count rate against time for these results.

[5]

A blank square of graph paper covered in fine squares, with heavier lines every ten squares. It carries no axes, no scales, no labels and no plotted points.

(ii) Use your graph to estimate the half-life for this material.

[1]

Half-life = .................................................. minutes

How did you do?

3c
3 marks

The isotope technetium-99 is a gamma emitter with a half-life of 6 hours. It is used as a radioactive tracer in medicine.

The technetium-99 is injected into a patient’s bloodstream and carried around the body by the blood. The radiation it emits is detected outside the body.

Explain why technetium-99 is suitable for use as a tracer in this way.

How did you do?

4a
2 marks

The photograph shows an old camera lens that contains several pieces of glass.

Photograph of an old camera lens seen at an angle. The front element is a large circle of curved glass held in a metal barrel, and several further pieces of glass can be seen inside it. The barrel is engraved with the lens name, a focal length of 5 cm and a maximum aperture of 1:2, and the ring behind it is marked with aperture numbers running from 2 to 8.

One of the pieces of glass includes a radioactive isotope, thorium-232.

Thorium-232 undergoes alpha decay and produces an isotope of radium, Ra.

Complete the equation for this decay.

An incomplete nuclear decay equation with empty boxes where numbers are missing. On the left, Th has 232 in a box above and to the left and 90 in a box below and to the left. An arrow points right to Ra, which has an empty box above and to the left and an empty box below and to the left. A plus sign follows, then the Greek letter alpha, with 4 in a box above and to the left and an empty box below and to the left.

How did you do?

4b
3 marks

The radioactive glass also emits beta particles from a different isotope. The diagram shows the position of the radioactive glass in the camera.

Cross-section diagram of the lens mount in the camera. Three discs of glass are stacked one above another inside a vertical-sided holder: the top disc is labelled ordinary glass, the shaded middle disc is labelled radioactive glass, and the bottom disc is also labelled ordinary glass. The holder stands on a wide hollow block labelled thick aluminium, which encloses the space beneath the glass.

Amateur astronomers sometimes remove an old camera lens to use as a lens in a homemade telescope.

(i) Suggest why it is safe to use radioactive glass in the camera as shown.

[1]

(ii) Suggest why an astronomer should not use a lens with radioactive glass close to their eye.

[2]

How did you do?

5a
1 mark

A teacher investigates the half-life of a radioactive isotope that decays quickly. 

The teacher measures the background activity.

Explain how this value should be used in the investigation.

How did you do?

5b
2 marks

Explain what is meant by the term half-life.

How did you do?

5c
3 marks

The graph shows how the activity of a sample of the radioactive isotope changes with time.

Graph of activity in Bq on the vertical axis, scaled 0 to 2500, against time in s on the horizontal axis, scaled 0 to 200. Eleven crosses are plotted on a fine grid and joined by a smooth decay curve: about 2400 Bq at 0 s, 1880 Bq at 20 s, 1450 Bq at 40 s, 1150 Bq at 60 s, 900 Bq at 80 s, 700 Bq at 100 s, 550 Bq at 120 s, 420 Bq at 140 s, 320 Bq at 160 s, 240 Bq at 180 s and about 190 Bq at 200 s.

(i) Use the graph to find the half-life of the isotope.

[2]

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

(ii) The teacher takes a new reading every 20 s. Suggest why the teacher measures the activity so frequently.

[1]

How did you do?

6a
5 marks

An unstable isotope of strontium has a half-life of 28.8 years.

It is a beta emitter and can be represented by this symbol.

Nuclear symbol for an isotope of strontium, with the mass number 90 above and to the left of the chemical symbol Sr, and the atomic number 38 below and to the left of Sr

(i) What is the mass number of this isotope?

[1]

(ii) Explain the meaning of the term half-life.

[2]

(iii) A person can absorb strontium atoms, which stay in their bones.

Explain why strontium-90 in the bones is a serious health hazard.

[2]

How did you do?

6b
4 marks

When a strontium-90 nucleus emits a beta particle, it decays to form yttrium-90.

Incomplete nuclear decay equation with empty boxes to be filled in. On the left is the chemical symbol Sr, with a box containing 90 above and to the left of it and a box containing 38 below and to the left of it. An arrow points right to the chemical symbol Y, which has an empty box above and to the left of it and a box containing 39 below and to the left of it. A plus sign follows, then the beta particle symbol beta with a superscript minus sign, which has an empty box above and to the left of it and an empty box below and to the left of it

(i) Complete the equation for this decay.

[2]

(ii) Yttrium-90 is also an unstable isotope.

Explain why strontium-90 and yttrium-90 can both be described as isotopes, even though they have different numbers of protons.

[2]

How did you do?

7
2 marks

lodine-131 is used to treat thyroid cancer. This radioactive isotope is allowed to enter the tumour.

Explain why iodine-131 is suitable for this treatment. 

How did you do?

8
3 marks

The diagram shows a machine which makes aluminium foil.

The machine uses a radioactive source to measure the thickness of the foil.

Line diagram of a machine that rolls aluminium foil. A thick horizontal sheet of metal travels in from the left, marked with a right-pointing arrow, and passes between two rollers, one above the sheet and one below it, labelled rollers. A curved arrow across the top of the upper roller points left and a curved arrow across the bottom of the lower roller points left, so the roller surfaces touching the sheet both move to the right. The sheet leaving the rollers on the right is drawn much thinner than the sheet entering on the left. Beyond the rollers a small container tapering downwards sits above the sheet, labelled radioactive source, and a small upright rectangle sits directly below the sheet, labelled detector. A right-pointing arrow on the thin sheet shows it travelling on to the right, where it winds onto a roll drawn as concentric dashed circles, labelled aluminium foil, with a curved arrow above the roll pointing clockwise.

The radioactive source emits beta particles. The output from the detector indicates the thickness of the foil.

Explain why beta particles are used, rather than alpha particles or gamma rays.

How did you do?

9a
3 marks

Thorium-232 decays into radon-220 through a number of alpha decays and beta decays.

The incomplete nuclear decay equation summarises this process.

Th90232 → Rn86220 + ...... α......   + ...... β−10

Complete the nuclear equation for the decay of thorium-232 into radon-220 by giving the missing numbers.

How did you do?

9b
5 marks

Radon-220 is a gas and an alpha emitter with a half-life of 55.6 s.

(i) State what is meant by the term half-life.

[1]

(ii) A sample of radon-220 has an initial activity of 760 Bq.

Calculate how long it takes for the activity of the sample to decrease to 95 Bq.

[2]

(iii) Explain why radon gas would be harmful if inhaled.

[2]

How did you do?

1
1 mark

Carbon-14 has a half-life of 5700 years. A sample of cloth contains 6.0 g of carbon-14.

What mass of carbon-14 will remain in the cloth after 11 400 years?

  • 1.5 g

  • 2.0 g

  • 2.5 g

  • 3.0 g

Choose your answer

2a
4 marks

The graph shows how the activity of tritium in a luminous sign varies with time.

Graph of activity in counts per minute against time in years for the tritium in a luminous sign. The vertical axis is labelled activity in counts per minute, scaled from 0 to 1200 in steps of 200 on a fine grid. The horizontal axis is labelled time in years, scaled from 0 to 40 in steps of 10. A smooth curve starts at 1200 counts per minute at 0 years and falls steeply at first and then more gradually, passing about 700 counts per minute at 10 years, about 420 at 20 years and about 260 at 30 years, and reaching about 150 counts per minute at 40 years.

(i) Explain what is meant by the term half-life.

[2]

(ii) Use the graph to estimate the half-life of tritium. Show your working.

[2]

How did you do?

2b
2 marks

The manufacturer of the luminous sign claims that the sign will work for more than 20 years. The minimum activity required for the tubes to emit sufficient light is 400 counts per minute.

Evaluate the manufacturer’s claim.

How did you do?

3a
2 marks

What is meant by the term half-life?

How did you do?

3b
2 marks

A doctor uses gamma radiation to produce an image of a person's brain.

A radioactive isotope called technetium-99m is used in this process. Technetium-99m emits gamma rays and has a short half-life.

A greyscale medical scan showing a horizontal cross-section through a patient's head, set on a black square background. Bright white bands trace the outline of the skull and curved structures inside the brain, showing where the most gamma radiation was detected, while mid-grey and dark-grey regions show where less was detected. There are no labels, scales or values on the image.

The doctor injects a solution of technetium-99m into the patient. A detector outside the patient received gamma radiation to form the image.

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

How did you do?

3c
5 marks

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

(i) Explain why the activity of a radioactive sample reduces with time.

[2]

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

[3]

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

How did you do?

4a
3 marks

A sample of sodium-24 has an activity of 1400 Bq. The half-life of sodium-24 is 15 hours.

On the axes, sketch a graph to show how the activity of this sample changes over the next 40 hours.

Blank grid graph with activity in Bq on the vertical axis, scaled 0 to 1600 in steps of 200, and time in hours on the horizontal axis, scaled 0 to 40 in steps of 5. No line is drawn on the grid.

How did you do?

4b
6 marks

Granite is a rock. It contains a radioactive isotope of uranium that decays very slowly.

(i) Explain how scientists can use this radioactivity to find the age of a piece of granite.

[4]

(ii) Suggest why the age of a piece of granite could not be found using a uranium isotope with a half-life of 15 hours.

[2]

How did you do?

5a
5 marks

A scientist placed a radioactive source in front of a Geiger-Muller detector and measured the count rate every 20 minutes.

The table shows her data.

A table with three columns headed Time in minutes, Count rate in counts per minute, and Corrected count rate in counts per minute. The rows read: 0, 660, 630; 20, 462, 432; 40, 330, 300; 60, 240, 210; 80, 180, 150; and 100, 142, 112.

The scientist corrects the count rate readings to allow for background radiation.

(i) State two sources of background radiation.

[2]

(ii) Describe how the scientist should measure the background radiation and correct the count rate readings.

[3]

How did you do?

5b
7 marks

(i) Plot a graph of the corrected count rate against time and draw the curve of best fit.

[5]

A blank sheet of graph paper with a fine square grid and heavier lines every ten small squares. There are no axes, scales or labels.

(ii) Use your graph to find the half-life of the radioactive source.

[2]

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

How did you do?

5c
5 marks

The scientist needs to reduce the risks when working with radioactive sources.

(i) Explain why radioactive sources can be dangerous.

[2]

(ii) Describe how the risks of working with radioactive sources can be reduced.

[3]

How did you do?