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Question 1
Two neutral atoms are represented by and .
What identifies these atoms as isotopes of the same element?
A.
They have different proton numbers and the same electron arrangement.
B.
They have the same number of neutrons and different numbers of protons.
C.
They have the same number of protons and different numbers of neutrons.
D.
They have the same nucleon number and different chemical properties.
Question 2
The binding energy per nucleon of nuclei increases steeply for small nucleon numbers and reaches a maximum near nucleon number .
Why can fusion of light nuclei release energy?
A.
The products have a greater total mass than the reactants.
B.
The nucleon number is not conserved during fusion.
C.
The strong nuclear force becomes repulsive for all light nuclei.
D.
The products have a greater total binding energy than the reactants.
Question 3
A sodium nucleus undergoes beta-plus decay.
What are the values of and for the neon nucleus?
A.
,
B.
,
C.
,
D.
,
Question 4
A manufacturer monitors the thickness of a moving aluminium sheet using a radioactive source and a detector on opposite sides of the sheet.
What type of radiation is most suitable?
A.
Alpha radiation, because it is stopped by small changes in aluminium thickness.
B.
Beta radiation, because its absorption changes appreciably with sheet thickness.
C.
Neutrino radiation, because it is weakly ionizing and easily detected.
D.
Gamma radiation, because it is completely absorbed by thin aluminium.
Question 5
Alpha-particle scattering from a nucleus agrees with the Coulomb model at large separations but deviates from it when the alpha particle approaches very close to the nucleus.
What conclusion is supported by this observation?
A.
Electrons inside the nucleus screen the nuclear charge at all distances.
B.
The alpha particle changes into a beta particle during the scattering.
C.
Gravitational attraction becomes comparable to the electrostatic force inside nuclei.
D.
A short-range nuclear interaction becomes significant at very small separations.
Question 6
A nuclide lies above the zone of stability on a neutron-number against proton-number plot.
What decay mode and nuclear change are most likely to move it towards stability?
A.
Beta-minus decay; decreases and increases.
B.
Alpha decay; increases and decreases.
C.
Gamma decay; both and decrease.
D.
Beta-plus decay; decreases and increases.
Question 7
For nucleon numbers greater than about , the binding energy per nucleon is approximately constant, with a slow decrease for the heaviest nuclei.
What does this approximate constancy suggest about the strong nuclear force?
A.
The electrostatic force between protons becomes attractive in heavy nuclei.
B.
Each nucleon interacts strongly mainly with nearby nucleons.
C.
Each nucleon attracts all other nucleons equally over long distances.
D.
The mass defect per nucleon is zero for all nuclei above nucleon number .
Question 8
A particular radioactive nuclide emits gamma photons with only certain well-defined energies.
What is this evidence for?
A.
The emitted photons have the same energy as visible light photons.
B.
The gamma photons are produced by electron transitions in the atom.
C.
The nucleus contains a continuous range of proton numbers.
D.
The nucleus has discrete energy levels.
Question 9
A nucleus of iodine is represented by the nuclide notation .
State what is meant by isotopes.
[1]
Determine the number of neutrons in this iodine nucleus.
[1]
Another isotope of iodine has 74 neutrons. State its nuclide notation.
[1]
0
Question 10
The total mass of the separated nucleons for a nucleus is . The mass of the nucleus is .
Using , what is the binding energy of the nucleus?
A.
B.
C.
D.
Question 11
A source has an observed count rate of . The background count rate is .
What observed count rate is expected after two half-lives, assuming the background count rate is unchanged?
A.
B.
C.
D.
Question 12
In beta-minus decay, the emitted beta particles from identical nuclei have a continuous range of kinetic energies up to a maximum value.
What accounts for this continuous spectrum?
A.
The parent nuclei have a continuous range of proton numbers before decay.
B.
The daughter nucleus emits gamma photons with every possible energy.
C.
The beta particles lose random amounts of energy only after leaving the detector.
D.
The available energy is shared among the beta particle, daughter nucleus and antineutrino.
Question 13
A radioactive sample has decay constant .
What fraction of the original undecayed nuclei remains after ?
A.
B.
C.
D.
Question 14
The graph shows the variation of average binding energy per nucleon with nucleon number.
State what a larger value of binding energy per nucleon indicates about a nucleus.
[1]
Explain, using the graph, why energy can be released when two light nuclei fuse.
[2]
0
Question 15
Some radioactive decay equations are shown with missing particles or nuclides.
Complete the alpha decay equation:
[1]
Complete the beta-minus decay equation:
[1]
nucleus emits a gamma photon. State the changes, if any, to its proton number and nucleon number.
[1]
0
Question 16
For nuclei with nucleon number greater than about 60, the binding energy per nucleon is approximately constant and decreases only slowly with increasing nucleon number.
Explain how this approximate constancy provides evidence that the strong nuclear force is short range.
[2]
State why very heavy nuclei can still release energy by rearranging into nuclei closer to the maximum of the binding-energy curve.
[1]
0
Question 17
The gamma-ray spectrum from an excited nucleus contains a small number of sharp lines rather than a continuous range of photon energies.
State what is meant by a discrete spectrum.
[1]
Explain why the sharp gamma-ray lines provide evidence for discrete nuclear energy levels.
[2]
0
Question 18
The table shows information about selected nuclides. Some entries are omitted. One of the nuclides is used in medical imaging and decays by beta-plus emission.
| Nuclide | Proton number (Z) | Nucleon number (A) |
|---|---|---|
| oxygen-16 | 8 | 16 |
| oxygen-18 | 8 | 18 |
| fluorine-18 | 9 | 18 |
Determine the neutron number of the oxygen nuclide with nucleon number 18 and identify one pair of isotopes from the table.
[2]
The nuclide fluorine-18 decays by beta-plus emission. Complete the nuclear equation for this decay, including the neutrino.
[2]
0
Question 19
Three sealed radioactive sources are tested by placing different absorbers between each source and a detector. The same geometry is used throughout.
| Source | No absorber / counts min^-1 | Paper / counts min^-1 | Aluminium / counts min^-1 |
|---|---|---|---|
| A | 2500 | 60 | 20 |
| B | 2400 | 2350 | 500 |
| C | 2300 | 2270 | 2230 |
Identify the source that emits mainly beta radiation. Justify your answer using the data.
[2]
Suggest which type of radiation is most suitable for monitoring the thickness of aluminium sheet in a factory.
[1]
Explain why an alpha-emitting source is more hazardous inside the body than outside the body.
[1]
0
Question 20
The nuclear mass of a lithium nucleus is . The proton mass is and the neutron mass is . Use .
State what is meant by nuclear binding energy.
[1]
Calculate the mass defect of the lithium nucleus.
[2]
Determine the binding energy of this lithium nucleus in MeV.
[1]
0
Question 21
A radioactive source is to be used to monitor the thickness of aluminium sheet as it passes between a source and a detector.
Suggest the most suitable type of radiation for this use.
[1]
Explain why alpha radiation and gamma radiation would be less suitable.
[2]
0
Question 22
A student measures the count rate from a radioactive source. The background count rate is .
State why the background count rate must be subtracted from the observed count rate.
[1]
At , the observed count rate is . Determine the corrected count rate at .
[1]
The corrected count rate is found to be after . Determine the half-life of the source.
[2]
0
Question 23
The scattering of alpha particles by a nucleus is compared with the prediction from electrostatic repulsion alone.
State the force responsible for the Coulomb prediction.
[1]
Explain how the observed deviation from the Coulomb prediction provides evidence for the strong nuclear force.
[2]
0
Question 24
A plot of neutron number against proton number shows the zone of stability. A nuclide X lies above the zone of stability and a nuclide Y lies below it.
State why stable nuclides with large proton number generally have .
[2]
Predict the likely decay mode of nuclide X and describe the change in and .
[1]
Predict the likely decay mode of nuclide Y.
[1]
0
Question 25
The kinetic energy spectrum of beta-minus particles emitted by one nuclide is continuous up to a maximum energy.
State the additional particle emitted in beta-minus decay.
[1]
Explain why a continuous beta spectrum is evidence for this additional particle.
[3]
0
Question 26
A student measures the count rate from a radioactive source using a Geiger-Muller tube. The background count rate is measured before the source is placed near the detector.
Calculate the corrected count rate at the start of the experiment.
[1]
Use the corrected count-rate data to determine the half-life of the source.
[2]
Explain why subtracting background radiation is especially important for the later readings in this experiment.
[2]
0
Question 27
The diagram shows how the strong nuclear force between two nucleons varies with separation. The electrostatic repulsion between two protons is also shown for comparison.
State the order of magnitude of the range of the strong nuclear force shown by the diagram.
[1]
Describe how the strong nuclear force and electrostatic force compare at large nuclear separations.
[1]
Explain why a nucleus containing several protons can be stable even though the protons repel each other electrically.
[2]
0
Question 28
The graph shows neutron number against proton number for stable nuclides. Three unstable nuclides, X, Y and W, are also shown.
Identify which of X and Y is neutron-rich and which is proton-rich.
[2]
Predict the most likely decay mode for nuclide X and state how its position changes on the against graph.
[2]
Explain why stable heavy nuclides generally have .
[1]
0
Question 29
The spectra from a radioactive nucleus are recorded. The alpha spectrum shows two sharp lines and the gamma spectrum shows one sharp line.
Determine the energy difference between the two alpha-particle peaks and compare it with the gamma photon energy.
[2]
Explain why sharp alpha and gamma peaks provide evidence for discrete nuclear energy levels.
[2]
State why this photon is classified as gamma radiation rather than an X-ray.
[1]
0
Question 30
A medical isotope has an initial activity of and a half-life of . A scan is performed after the isotope is prepared.
Determine the decay constant of the isotope in .
[1]
Calculate the activity at the time of the scan.
[2]
State the condition under which is a good approximation to the probability that one nucleus decays in the time interval .
[1]
0
Question 31
The graph shows the variation of average binding energy per nucleon with nucleon number. A small table gives binding-energy data for deuterium, tritium and helium-4.
State the approximate nucleon number at which the binding energy per nucleon is greatest.
[1]
Use the inset data to calculate the energy released in the reaction .
[3]
Explain why this reaction releases energy in terms of binding energy.
[1]
0
Question 32
A proton may react with lithium-7 to produce two alpha particles. Atomic masses for the neutral atoms involved are provided. Electron masses cancel in this calculation.
| Species | Atomic mass / u |
|---|---|
| hydrogen-1 atom | 1.0078 |
| lithium-7 atom | 7.0160 |
| helium-4 atom | 4.0026 |
Calculate the mass decrease in this reaction in unified atomic mass units.
[2]
Calculate the energy released in MeV.
[1]
State the main form in which the released energy appears.
[1]
0
Question 33
High-energy electrons are scattered by a thin metal foil. The angle of the first diffraction minimum is used to estimate the nuclear diameter using , where is in radians, is the electron de Broglie wavelength and is the nuclear diameter.
Use the graph to estimate the nuclear diameter of the metal nucleus.
[2]
Explain why the observation of a diffraction minimum provides evidence about nuclear size.
[1]
State how scattering experiments provide evidence for an interaction other than electrostatic repulsion at very small nuclear separations.
[1]
0
Question 34
The graph shows the binding energy per nucleon for nuclides with nucleon number greater than 40. A possible fission of a uranium nucleus into two similar fragments is indicated.
Describe the trend in binding energy per nucleon for nucleon numbers greater than about 60.
[1]
Estimate the energy released if a uranium-236 nucleus splits into two fragments of nucleon number about 118.
[2]
Explain how the approximate constancy of the curve for large nucleon number is evidence for the short range of the strong nuclear force.
[2]
0
Question 35
A beta-minus spectrum and an alpha spectrum are recorded using the same energy detector. The parent nuclei are initially at rest.
Describe the difference between the beta-minus spectrum and the alpha spectrum.
[1]
Explain why a two-product model of beta-minus decay cannot account for the observed beta spectrum.
[2]
Identify the additional particle emitted in beta-minus decay.
[1]
0
Question 36
A sample contains a radioactive isotope of radium. Part of its decay chain is represented on a chart of nucleon number against proton number .
The nuclide is written as .
I.
Determine the number of neutrons in .
[1]
II.
State what is meant by isotopes.
[1]
The first decay in the chain is alpha decay.
I.
Complete the nuclear equation for the alpha decay of .
[1]
II.
Explain why the alpha decay arrow has the direction shown on an against chart.
[1]
Explain the changes shown by the beta-minus decay and subsequent gamma emission on the against chart.
[3]
0
Question 37
A student measures the count rate from a beta-emitting source using a Geiger-Muller tube. The background count rate is measured before the source is placed near the detector. The graph shows the observed count rate against time.
Consider the measurement procedure.
I.
Distinguish between activity and count rate.
[1]
II.
Explain why the observed count rate is not equal to the activity of the source.
[1]
The observed count rate is at and at . The background count rate is .
I.
Determine the corrected count rates at and at .
[1]
II.
Determine the half-life of the source using these readings.
[2]
Evaluate the reliability of using late-time readings to determine the half-life in this experiment.
[2]
0
Question 38
A hospital and an engineering company are selecting radioactive sources for different applications. The available emissions are alpha, beta-minus and gamma radiation.
Compare alpha, beta-minus and gamma radiation in matter.
I.
Compare their ionizing abilities.
[1]
II.
Compare their penetrating abilities and give one suitable absorber for each.
[2]
beta source is proposed for monitoring the thickness of aluminium sheet as it is manufactured.
I.
Explain why beta radiation is suitable for monitoring the thickness of aluminium sheet as it is manufactured.
[1]
II.
Explain why alpha and gamma radiation would be less suitable for monitoring the thickness of aluminium sheet as it is manufactured.
[1]
Evaluate two factors, in addition to emission type, that should be considered when choosing a radioactive tracer for a medical scan.
[2]
0
Question 39
A sample of a medical isotope is monitored after preparation. The corrected count rate is proportional to the activity. A graph of against time is plotted, where is the corrected count rate.
Use the graph to determine the decay constant in .
[2]
Calculate the half-life of the isotope.
[1]
Calculate the fraction of the initial activity remaining after .
[1]
student says that the probability of one nucleus decaying in the next is approximately . Evaluate this statement.
[1]
0
Question 40
A deuterium nucleus, , can be considered to be formed from a separate proton and neutron. The mass of a proton is , the mass of a neutron is and the mass of a deuterium nucleus is .
Consider the formation of the deuterium nucleus.
I.
Define nuclear binding energy.
[1]
II.
Calculate the mass defect of the deuterium nucleus in .
[2]
The conversion factor is .
I.
Calculate the binding energy of the deuterium nucleus in .
[2]
Discuss the significance of the mass defect in this example.
[3]
0
Question 41
The graph shows the variation of average binding energy per nucleon with nucleon number.
Interpret the curve for selected nuclei.
I.
State what is meant by average binding energy per nucleon.
[1]
II.
Explain why nuclei near the maximum of the curve are relatively stable.
[2]
Use the curve to compare possible energy release mechanisms.
I.
Explain why fusion of very light nuclei can release energy.
[1]
II.
Explain why alpha decay of a very heavy nucleus can release energy.
[1]
Discuss why the curve is evidence that nuclear stability is not determined only by the electrostatic force.
[2]
0
Question 42
A sealed radioactive source contains a large number of identical unstable nuclei. The source is kept at different temperatures while its count rate is measured.
| Elapsed time / h | Corrected count rate at 20 °C / s^-1 | Corrected count rate at 80 °C / s^-1 |
|---|---|---|
| 0 | 640 | 640 |
| 12 | 320 | 320 |
| 24 | 160 | 160 |
| 36 | 80 | 80 |
| 48 | 40 | 40 |
Consider the nature of radioactive decay.
I.
State what is meant by random radioactive decay.
[1]
II.
Explain what is meant by spontaneous radioactive decay.
[1]
III.
Explain why a predictable half-life can be measured even though individual decays are random.
[1]
source has an initial corrected count rate of and a half-life of .
I.
Determine the corrected count rate after .
[1]
II.
Determine the fraction of parent nuclei remaining after .
[1]
Explain how the strong nuclear force contributes to the existence of nuclei that contain more than one proton.
[2]
0
Question 43
High-energy electrons are scattered by nuclei. For one experiment, the electron de Broglie wavelength is and the first diffraction minimum occurs at . The first diffraction minimum occurs at an angle that is approximately related to the electron de Broglie wavelength and the nuclear diameter by .
An electron beam has de Broglie wavelength . The first minimum is observed at .
I.
Determine the nuclear diameter.
[2]
II.
Explain why electrons can be used to probe nuclear size in this experiment.
[1]
Alpha-particle scattering from some nuclei deviates from the prediction of a purely electrostatic model when the alpha particles approach very close to the nucleus.
I.
Explain why this deviation is evidence for the strong nuclear force.
[2]
Evaluate how scattering evidence and binding-energy evidence together support the model of a short-range attractive strong nuclear force.
[2]
0
Question 44
The diagram shows a simplified neutron number against proton number plot. The shaded band represents the zone of stability.
Consider the shape of the zone of stability.
I.
State the approximate relationship between and for stable light nuclides.
[1]
II.
Explain why stable heavy nuclides have .
[2]
Nuclide is above the zone of stability and nuclide is below it.
I.
Predict the likely decay mode of and describe its movement on the - plot.
[1]
II.
Predict the likely decay mode of and describe its movement on the - plot.
[1]
Discuss why a very heavy nuclide may undergo alpha decay even if beta decay could change its neutron-to-proton ratio.
[2]
0
Question 45
An excited daughter nucleus formed in an alpha decay subsequently emits gamma photons. Measurements of the alpha particles and gamma photons are shown as spectra.
Consider the gamma spectrum.
I.
Explain why the observation of discrete gamma photon energies provides evidence for discrete nuclear energy levels.
[2]
II.
gamma photon has energy . Calculate its energy in joules.
[1]
Consider the alpha spectrum from the same decay.
I.
Explain why alpha particles from one nuclide can have a small number of well-defined kinetic energies.
[2]
Compare the origin of gamma photons and X-ray photons, noting that their energy ranges may overlap.
[2]
0
Question 46
The beta-minus decay of a nucleus produces a daughter nucleus, an electron and an antineutrino. The measured electron energies form a continuous beta spectrum.
Consider the beta-minus decay equation.
I.
Complete the general equation for beta-minus decay using and as nuclear symbols.
[2]
II.
State one property of the antineutrino that makes it difficult to detect.
[1]
Discuss the significance of the continuous beta spectrum.
I.
Explain why a two-particle model of beta decay would conflict with the observed spectrum.
[1]
II.
Explain how the antineutrino resolves this conflict.
[1]
Compare the beta spectrum with the alpha spectrum shown in the inset.
[2]
0
Question 47
A radioactive isotope used in a laboratory has an initial corrected count rate of . After the corrected count rate is . The detector geometry remains unchanged.
| Time / h | Corrected count rate / s^-1 |
|---|---|
| 0.0 | 480 |
| 5.0 | 150 |
Use the radioactive decay law for this isotope.
I.
Show that the decay constant is approximately .
[2]
II.
Determine the half-life of the isotope.
[1]
III.
Calculate the corrected count rate after .
[1]
The same data are analysed by plotting the natural logarithm of the corrected count rate against time.
I.
Explain why this graph should be a straight line.
[1]
II.
State how the half-life is obtained from the gradient of this graph.
[1]
Evaluate one advantage of the exponential method over using only integer half-lives for this set of data.
[2]
0
Question 48
A sample of a long-lived radioactive isotope has mass and molar mass . Its activity is measured to be . Assume the sample is pure.
Determine properties of the isotope from the sample data. Use .
I.
Calculate the number of undecayed nuclei in the sample.
[2]
II.
Calculate the decay constant of the isotope.
[1]
III.
Determine the half-life in years.
[2]
The decay constant is sometimes described as the probability per unit time that a nucleus decays.
[1]
Evaluate why this method can be used for an isotope with a half-life that is too long to measure by observing the activity halve directly.
[2]
0
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