Radioactive decay and nuclear radiation

Figure 12 is a diagram of part of a water wave.

Use data from Figure 12 to determine the amplitude of the wave.

Use data from Figure 12 to determine the wavelength of the wave.

wavelength =_........

The water wave shown in Figure 12 is generated in a large tank.

A student observes the wave.

Describe how the student could determine the wave speed of the wave.

When an earthquake happens, waves are transmitted through the Earth. Figure 13 is a diagram of a part of the Earth’s crust.

Earth’s surface

An earthquake happens at point X, 20 km below the Earth’s surface.

An earthquake wave from X is detected at point L.

This earthquake wave is a transverse wave.

State one other example of a transverse wave.

A point in the crust is labelled R in Figure 13. There is a rock at point R.

Describe the effect that this earthquake wave has on the rock at R as the wave passes through the rock.

You may add to Figure 13 to help your answer.

*(c) A scientist investigates a sample of an unknown radioactive material.

The scientist finds that the sample does not emit beta radiation.

The scientist sets up the experiment shown in Figure 14 and uses different absorbers to investigate alpha and gamma radiation.

The results are shown in Figure 15.

The count rates are rounded to two significant figures.

The background radiation was 18 counts per minute (cpm).

Discuss whether the sample emits alpha or gamma radiation or both.

Your answer should refer to

• the data shown in Figure 15

• how the data gives evidence for particular radiations.

Carbon-14 is a radioactive substance that emits beta minus (β^–) particles.

Which of these is the unit for the activity of a sample of carbon-14?

Which row of the table gives a correct comparison of the penetrating abilities of alpha, beta and gamma radiation?

The mass of a beta minus particle is 9.1 × 10^–31kg.

Calculate the kinetic energy of a beta minus particle moving with a speed of 3.8 × 10⁶m / s.

kinetic energy =_........

Describe what happens in the nucleus of an atom when a beta plus particle is emitted.

*(c) Radioactive decay can produce gamma radiation and alpha radiation.

Compare the processes of gamma decay and alpha decay.

Your answer should include

• a description of both gamma radiation and alpha radiation

• the effect of each type of decay on the original nucleus.

Figure 6 is a diagram representing an atom.

Write the names of the particles X, Y and Z on the lines next to each letter in Figure 6.

The nucleus of a different atom emits a gamma ray.

What happens to the number of particles in the nucleus?

A teacher demonstrates a radioactivity experiment to a class of students.

The teacher places a radioactive source in front of a radiation detector.

State one safety precaution the teacher should take.

The teacher uses the detector to measure the activity of the source several times.

Figure 7 shows the results.

The teacher tells the class that radioactive decay is random.

State how the data in Figure 7 supports this statement.

Calculate the mean of the four measurements in Figure 7.

mean =_........ Bq

The teacher moves the radiation detector to different distances from the radioactive source.

The teacher determines the mean detector reading at each distance from the source.

The teacher plots the results on graph paper, as shown in Figure 8.

The source emits alpha radiation only.

Explain how the graph in Figure 8 shows that the source only emits alpha radiation.

Give a reason why the mean detector reading in Figure 8 does not fall to zero in this experiment.

An electron has a charge of –1.

The charge on an alpha particle is

Alpha, beta and gamma are all ionising radiations.

Give the meaning of the term ionising.

A teacher determines the background radiation count rate in a laboratory.

Explain how to determine a value for the background radiation count rate.

The teacher now investigates the absorption of beta radiation by different thicknesses of aluminium.

The apparatus available is

• a source of beta radiation

• a Geiger–Müller (G-M) tube and counter

• 10 pieces of aluminium, each 0.5 mm thick

• a metre rule.

Sketch a labelled diagram showing the positions of the apparatus when the measurements are being taken.

Give the independent variable in this investigation.

Name a quantity that must be kept constant during the investigation.

Strontium-90 is the source of beta minus radiation in this investigation.

Complete the nuclear equation for this emission of beta minus radiation.

Figure 7 shows a safety sign on the door of a laboratory where radioactive materials are used.

State one way that radioactivity can be dangerous to humans.

State one piece of equipment that can be used to measure radioactivity.

Alpha (α) radiation and ultraviolet (UV) radiation are ionising radiations.

Give two other ionising radiations.

A sample of a radioactive isotope has a mass of 520 g.

The half‑life of the radioactive isotope is 18 days.

Calculate the mass of the original radioactive isotope remaining after 18 days.

mass after 18 days_........ g

Calculate the mass of the original radioactive isotope remaining after 54 days.

mass after 54 days_........ g

This question is about radioactivity.

Alpha (α), beta (β) and gamma (γ) are three types of radioactive emissions.

Which statement describes all of these radioactive emissions?

Fluorine-19 is a stable isotope of the element fluorine.

The element fluorine also has several radioactive isotopes.

Describe one similarity and one difference between the numbers of particles in one nucleus of fluorine-19 and one nucleus of a radioactive isotope of fluorine.

similarity_........

Figure 10 shows a Geiger–Muller (G–M) tube attached to a counter. The G–M tube is used to measure the activity of a source of beta (β) radiation. There is an aluminium sheet between the beta source and the G–M tube. The counter is switched on and after 1 minute shows a count of 268.

The aluminium sheet is taken away. The counter is reset to zero and then switched on again. A new count is taken for 1 minute.

Explain why the new count is greater than 268.

The beta source is then also taken away. The counter is reset to zero and switched on again. A new count is taken for 1 minute.

Give a reason why there would now be a reading on the counter.

State the SI unit for the activity of a radioactive source.

*(d) Exposing people to radioactive sources can be dangerous.

Describe the dangers of exposure to radioactive sources and what can be done to protect hospital staff when they are working with radioactive sources.

Equations

This question is about radioactivity.

Alpha (α), beta (β) and gamma (γ) are three types of radioactive emissions.

Which statement describes all of these radioactive emissions?

Fluorine-19 is a stable isotope of the element fluorine.

The element fluorine also has several radioactive isotopes.

Describe one similarity and one difference between the numbers of particles in one nucleus of fluorine-19 and one nucleus of a radioactive isotope of fluorine.

similarity_........

Figure 3 shows a Geiger–Muller (G–M) tube attached to a counter. The G–M tube is used to measure the activity of a source of beta (β) radiation. There is an aluminium sheet between the beta source and the G–M tube. The counter is switched on and after 1 minute shows a count of 268.

The aluminium sheet is taken away. The counter is reset to zero and then switched on again. A new count is taken for 1 minute.

Explain why the new count is greater than 268.

The beta source is then also taken away. The counter is reset to zero and switched on again. A new count is taken for 1 minute.

Give a reason why there would now be a reading on the counter.

State the SI unit for the activity of a radioactive source.

Radium-223 is a radioactive substance.

Radium-223 is an alpha emitter.

The half-life of radium-223 is 11 days.

A radioactive source contains 1.7 × 10²³ nuclei of radium-223.

Calculate the number of radium-223 nuclei remaining in the source after a time of 33 days.

number of radium-223 nuclei remaining =_........

Sometimes food can become contaminated with radioactive substances.

Describe the harmful effects of eating food contaminated with radioactive substances.

Gamma radiation can be used in food processing to irradiate food.

Explain why some food is irradiated with gamma radiation.

Gamma radiation is part of the electromagnetic spectrum.

When the nucleus of an atom emits a gamma ray, the number of protons in the nucleus and the number of neutrons in the nucleus do not change.

State how the nucleus does change when it emits a gamma ray.

*(d) Gamma radiation is produced by radioactive decay.

Alpha radiation and beta radiation are also produced by radioactive decay.

Compare the processes of alpha decay and beta decay.

Your answer should include what each radiation is and what effect each decay has on the original nucleus.

How many protons are in the nucleus of an atom of strontium‑90?

How many neutrons are in the nucleus of an atom of strontium‑90?

The half‑life of strontium‑90 is 29 years.

The table in Figure 4 gives some information about how the mass of a sample of strontium‑90 changes with time.

Complete the table in Figure 4.

A teacher sets up an experiment to show some students how far beta particles travel in air.

Figure 5 shows some of the equipment she uses.

State the scientific name for the radioactivity detector shown in Figure 5.

The teacher also has:

• a radioactive source that emits only beta particles

• a metre rule.

State two precautions the teacher must take to protect herself from the effects of radioactivity.

Describe how the teacher could show how far beta particles travel in air.

Which of these describes isotopes of an element?

Figure 7 represents a decay that can happen inside the nucleus of an atom.

Which decay is represented in Figure 7?

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

A school cobalt source had an activity of 38.5 kBq in the year 2000.

Estimate the activity of this source in the year 2020.

activity =_........ kBq

Explain what can happen to the body if a person has a prolonged exposure to gamma rays.

Calculate the average count rate, in counts / s, from the graph.

Show your working on the graph.

average count rate =_........ counts / s

The student says that the experiment must have been done carelessly because the data seemed quite scattered away from the best fit line.

The teacher claims such results should be expected in radioactivity experiments.

Justify the teacher’s claim.

Carbon-13 and carbon-14 are isotopes of carbon.

Nuclei of carbon-13 and carbon-14 can be represented by these symbols

13 14

Complete the table for an atom of carbon-13 and an atom of carbon-14.

State the name of an instrument that can be used to measure radioactivity.

State two sources of background radiation.

Carbon-14 is radioactive and has a half-life of 5 700 years.

The number of radioactive carbon-14 atoms in a very old piece of wood is found to have decreased from 1 000 000 to 125 000.

Determine the age of the piece of wood.

age of wood =_........ years

Carbon-14 decays into nitrogen-14.

The symbol for nitrogen-14 is¹⁴₇N

Explain what happens in a carbon-14 nucleus when it decays to a nitrogen-14 nucleus.

Figure 10 shows a Geiger‑Müller (GM) tube used for measuring radioactivity.

Describe how a teacher should use a Geiger‑Müller (GM) tube to compare the count‑rates from two different radioactive rocks.

A hospital uses a radioactive isotope with a half‑life of 6 hours.

A technician measures a count rate of 80 counts per minute (cpm) from this isotope.

Complete the graph on Figure 11, as accurately as possible, to show how the count‑rate from this isotope will change from the time of the first measurement.

The first point is already drawn in Figure 11.

*(c) A radioactive rock is placed near to the front of a Geiger‑Müller (GM) tube. A radioactivity count‑rate is first made in air.

The count‑rate is measured again with each of three different absorbers between the rock and the GM tube.

Figure 12 shows the count‑rates measured.

A scientist has an idea that the rock emits three different types of radiation.

Explain how the data in this table supports the scientist’s idea.

Figure 3 shows a Geiger-Müller (GM) tube used for measuring radioactivity.

Figure 3

Describe how a teacher should use a Geiger-Müller (GM) tube to compare the count-rates from two different radioactive rocks.

A hospital uses a radioactive isotope with a half-life of 6 hours.

A technician measures a count rate of 80 counts per minute (cpm) from this isotope.

Complete the graph on Figure 4, as accurately as possible, to show how the count‑rate from this isotope will change from the time of the first measurement.

The first point is already drawn in Figure 4.

One radioactive source used in hospitals is technetium (Tc).

Technetium is produced from the radioactive decay of molybdenum (Mo).

Complete the following nuclear equation.