T7-2
1.
[233 marks]
Nucleus P decays by a sequence of emissions to form nucleus Q. One
during the sequence. Which statement is correct?
α particle and two β− particles are emitted
[1 mark]
A. Nucleus P has the same number of neutrons as nucleus Q.
B. Nucleus P is an isotope of nucleus Q.
C. Nucleus P has a greater charge than nucleus Q.
D. Nucleus P has fewer protons than nucleus Q.
2.
In a nuclear fission reaction, nucleus X splits into nucleus Y and nucleus Z. Which of the following gives a possible [1 mark]
order of the nuclei from lowest to highest binding energy per nucleon?
A. Z → Y → X
B. Z → X → Y
C. Y → X → Z
D. X → Z → Y
3.
Some of the energy levels for a hydrogen atom are shown in the diagram.
[1 mark]
The table shows four photons with their corresponding energies.
Each photon is incident on a hydrogen atom in its ground state. Which photons could be absorbed by the atom?
A. W only
B. X and Y only
C. Y and Z only
D. X, Y and Z only
4.
Geiger and Marsden bombarded a thin gold foil with alpha particles. They observed that a small fraction of the
[1 mark]
alpha particles were deflected through angles greater than 90˚. What does this observation suggest about the nucleus?
A. It is at the centre of the atom.
B. It is surrounded by orbiting electrons.
C. It is made of protons and neutrons.
D. It is a small region of the atom and is positively charged.
5.
What is the relationship between nucleon number A, proton number Z and neutron number N?
[1 mark]
A. A=Z=N
B. A+Z=N
C. A−Z=N
D. Z−A=N
6.
The initial number of atoms in a pure radioactive sample is N. The radioactive half-life of the sample is defined as [1 mark]
the
A. time taken for one atom to undergo decay.
B. probability for
N
atoms to undergo decay.
2
C. time taken for
N
atoms to undergo decay.
2
D. probability that one atom will decay per unit time.
7.
The structure of the atom was investigated by firing alpha particles from a source at a thin foil of gold. The basic
set-up of the apparatus is shown.
Which graph shows the variation in the number of scattered alpha particles with scattering angle θ?
[1 mark]
This question is in two parts. Part 1 is about kinematics and gravitation. Part 2 is about radioactivity.
Part 1 Kinematics and gravitation
A ball is released near the surface of the Moon at time t=0. The point of release is on a straight line between the
centre of Earth and the centre of the Moon. The graph below shows the variation with time t of the displacement s of
the ball from the point of release.
8a.
8b.
State the significance of the negative values of s.
Use the graph to
(i) estimate the velocity of the ball at t = 0.80 s.
(ii) calculate a value for the acceleration of free fall close to the surface of the Moon.
[1 mark]
[6 marks]
8c.
The following data are available.
[4 marks]
Mass of the ball = 0.20 kg
Mean radius of the Moon = 1.74 × 106 m
Mean orbital radius of the Moon about the centre of Earth = 3.84 × 108 m
Mass of Earth = 5.97 × 1024 kg
Show that Earth has no significant effect on the acceleration of the ball.
8d.
Calculate the speed of an identical ball when it falls 3.0 m from rest close to the surface of Earth. Ignore air
resistance.
[1 mark]
8e.
Sketch, on the graph, the variation with time t of the displacement s from the point of release of the ball when the [3 marks]
ball is dropped close to the surface of Earth. (For this sketch take the direction towards the Earth as being negative.)
Part 2 Radioactivity
Two isotopes of calcium are calcium-40 (
radioactive with a half-life of 4.5 days.
8f.
40
Ca) and calcium-47
20
( 47
Ca). Calcium-40 is stable and calcium-47 is
20
Calculate the percentage of a sample of calcium-47 that decays in 27 days.
47
8g. The nuclear equation for the decay of calcium-47 into scandium-47 (21 Sc) is given by
47 Ca
20
0
→ 47
21 Sc+−1 e + X
(i) Identify X.
(ii) The following data are available.
Mass of calcium-47 nucleus = 46.95455 u
Mass of scandium-47 nucleus = 46.95241 u
Using the data, determine the maximum kinetic energy, in MeV, of the products in the decay of calcium-47.
(iii) State why the kinetic energy will be less than your value in (h)(ii).
[3 marks]
[4 marks]
Part 2 Radioactivity
Radium-224 (224
88 RA) is a radioactive nuclide that decays to form radon-220. Radon-220 is itself radioactive and
undergoes a further decay. The table shows the series of radioactive nuclides that are formed as the decays proceed.
The series ends with a stable isotope of lead.
9a.
For the final thallium nuclide, identify the
[2 marks]
(i) nucleon number.
(ii) proton number.
9b.
Radon-220 is a radioactive gas. It is released by rocks such as granite. In some parts of the world, houses are
[2 marks]
built from materials containing granite. Explain why it is unlikely that radon-220 will build up in sufficient quantity to be
harmful in these houses.
−1
9c.
(i) Calculate, in hour−1, the decay constant of lead-212.
(ii) In a pure sample of lead-212 at one instant, 8.0 ×
that remains after a period of 35 hours.
10−3
[6 marks]
kg of the lead-212 is present. Calculate the mass of lead-212
(iii) A sample of pure radium begins to decay by the series shown in the table. At one instant, a mass of 8.0 × 10−3 kg of
lead-212 is present in the sample. Suggest why, after 35 hours, there will be a greater mass of lead-212 present in the
sample than the value you calculated in (h)(ii).
This question is in two parts. Part 1 is about renewable energy. Part 2 is about nuclear energy and radioactivity.
Part 1 Renewable energy
A small coastal community decides to use a wind farm consisting of five identical wind turbines to generate part of its
energy. At the proposed site, the average wind speed is 8.5ms–1 and the density of air is 1.3kgm –3. The maximum
power required from the wind farm is 0.75 MW. Each turbine has an efficiency of 30%.
10a.
(i) Determine the diameter that will be required for the turbine blades to achieve the maximum power of 0.75
MW.
[8 marks]
(ii) State one reason why, in practice, a diameter larger than your answer to (a)(i) is required.
(iii) Outline why the individual turbines should not be placed close to each other.
(iv) Some members of the community propose that the wind farm should be located at sea rather than on land. Evaluate
this proposal.
10b.
Currently, a nearby coal-fired power station generates energy for the community. Less coal will be burnt at the [7 marks]
power station if the wind farm is constructed.
(i) The energy density of coal is 35 MJ kg–1. Estimate the minimum mass of coal that can be saved every hour when the
wind farm is producing its full output.
(ii) One advantage of the reduction in coal consumption is that less carbon dioxide will be released into the atmosphere.
State one other advantage and one disadvantage of constructing the wind farm.
(iii) Suggest the likely effect on the Earth’s temperature of a reduction in the concentration of atmospheric greenhouse
gases.
Part 2 Nuclear energy and radioactivity
The graph shows the variation of binding energy per nucleon with nucleon number. The position for uranium-235 (U235) is shown.
10c. State what is meant by the binding energy of a nucleus.
[1 mark]
10d.
(i) On the axes, sketch a graph showing the variation of nucleon number with the binding energy per nucleon.
[5 marks]
(ii) Explain, with reference to your graph, why energy is released during fission of U-235.
235
10e. U-235 (92 U) can undergo alpha decay to form an isotope of thorium (Th).
[4 marks]
(i) State the nuclear equation for this decay.
(ii) Define the term radioactive half-life.
(iii) A sample of rock contains a mass of 5.6 mg of U-235 at the present day. The half-life of U-235 is 7.0×108 years.
Calculate the initial mass of the U-235 if the rock sample was formed 2.1×109 years ago.
This question is about quarks.
An interaction between an electron and a positron can lead to the production of hadrons via the reaction
e− + e+ → u + ū
where u is an up quark. This process involves the electromagnetic interaction.
11a.
11b.
Draw a Feynman diagram for this interaction.
[2 marks]
Outline, with reference to the strong interaction, why hadrons are produced in the reaction.
[2 marks]
This question is about particles and interactions.
12.
When a free neutron decays to a proton, an electron is one of the decay products.
[2 marks]
(i) State the name of the exchange particle and the interaction involved in this decay.
(ii) The interaction and the exchange particle in (a)(i) may arise when a quark decays. Describe the change in the quark
structure of the neutron.
This question is about a K meson decay.
The positive kaon K+ has a strangeness of +1. It can decay through the interaction
K+ → μ+ + νμ.
Charge, energy and momentum are conserved in this decay.
13a.
13b.
State the quark structure of the K+.
Deduce one further quantity in this decay that is
[1 mark]
[2 marks]
(i) conserved.
(ii) not conserved.
This question is about the hydrogen atom.
The diagram shows the three lowest energy levels of a hydrogen atom.
14a.
14b.
An electron is excited to the n=3 energy level. On the diagram, draw arrows to show the possible electron
transitions that can lead to the emission of a photon.
[2 marks]
Show that a photon of wavelength 656 nm can be emitted from a hydrogen atom.
[2 marks]
This question is about particles and interactions.
15a. (i) State what is meant by an antiparticle.
[3 marks]
(ii) Some particles are identical to their antiparticles. Discuss whether the neutron and the antineutron are identical.
−
→
++ −+ −
15b.
The Feynman diagram represents the decay K −
→ π + +π − +π − .
[5 marks]
Particles X and Y are exchange particles.
(i) Explain what is meant by an exchange particle.
(ii) Identify X.
(iii) Determine the electric charge of Y.
(iv) Calculate the change in strangeness in the decay of the K – .
This question is about the standard model and the Pauli exclusion principle.
16a.
State one conservation law that would be violated, if the following reactions were to occur.
(i) π 0
(ii) p+
→
e+
+
μ−
+ n̄ → e+ + e− + v̄e + ve
[2 marks]
16b.
The reaction v̄μ
+ e− → v̄μ + e−
is an example of a neutral current reaction. Draw a Feynman diagram for
[3 marks]
this reaction labelling all the particles involved. The arrow provided indicates the direction of time.
3
17. The binding energy per nucleon of a 1 H nucleus is 3 MeV. What is the minimum energy needed to
completely separate the nucleons of 31 H?
[1 mark]
A. 12 MeV
B. 9 MeV
C. 6 MeV
D. 3 MeV
2
3
18. The nuclear reaction 1 H + 1 H
A. alpha decay.
B. nuclear fission.
C. nuclear fusion.
D. neutron capture.
→ 42 He+10 n would best be described as
[1 mark]
2
3
19. A student suggests the following nuclear reaction between deuterium 1 H and tritium 1 H
2H + 3H
1
1
[1 mark]
→ nX + mY
where n and m are integers. What are X and Y?
20.
In a neutral atom there are ne electrons, np protons and nn neutrons. What is the mass number of the nuclide?
[1 mark]
A. np + ne + nn
B. np + nn
C. nn + np – ne
D. nn – ne
21.
22.
A radioactive nuclide decays to a stable daughter nuclide. Initially the sample consists entirely of atoms of the
radioactive nuclide. What fraction of the sample consists of the daughter nuclide after four half-lives?
A.
15
16
B.
1
16
C.
1
8
D.
7
8
A radioactive sample has activity A 0 at t=0. What will be the activity of the sample after two half-lives?
A. zero
B.
A0
4
A0
if the sample is kept at high pressure
4
A0
D. greater than
if the sample is kept at high temperature
4
C. less than
[1 mark]
[1 mark]
23.
The arrows below indicate transitions involving three energy levels of an atom. The wavelength of the photon
emitted in each transition is indicated.
Which of the following relationships between the wavelengths is correct?
A. λ1
= λ2 + λ3
B. λ1
= λ3 − λ2
C.
1
λ1
=
1
λ2
+
1
λ3
D.
1
λ1
=
1
λ2
−
1
λ3
[1 mark]
24.
The graph shows the variation with time t of the activity A of a radioactive sample. The energy released in each
decay is E. The shaded area is equal to S.
[1 mark]
What does the quantity S × E represent?
A. Average energy produced in 2 s.
B. Average power produced in 2 s.
C. Total energy produced in 2 s.
D. Maximum power produced in 2 s.
25.
An alpha particle is directed head-on towards a nucleus of an isotope of iron. A second alpha particle, with the
same energy as the first, is directed head-on towards a different isotope of iron.
[1 mark]
Which of the following is a comparison of the distances of closest approach of the two alpha particles and the forces
experienced by the alpha particles at the point of closest approach?
26.
27.
The de Broglie wavelength of an electron is equal to the wavelength of a photon that has energy E. What is the
momentum of the electron?
A.
E
c
B.
E
hc
C.
hc
E
D.
me c2
hE
Which of the following provides evidence for the existence of atomic energy levels?
[1 mark]
[1 mark]
A. Absorption spectra
B. Nuclear fission
C. The Geiger–Marsden experiment
D. Radioactive decay
28.
What is the definition of the unified atomic mass unit?
[1 mark]
A. The mass of one atom of hydrogen.
B.
1
of the mass of an atom of carbon-12.
12
C. The mass of one atom of carbon-12.
D.
29.
1
of the mass of an atom of oxygen-16.
16
Nuclei of the isotope nitrogen-14 are bombarded with neutrons and as a result nuclei of an isotope of carbon are [1 mark]
produced. The nuclear reaction equation for this process may be written as
14 N +
7
neutron → A
6 C + proton
What is the nucleon number A of the isotope of carbon?
A. 12
B. 13
C. 14
D. 15
30.
The diagram shows four energy levels W, X, Y and Z of an atom.
[1 mark]
Which electron transition will produce a photon of the longest wavelength and which transition will produce a photon with
the highest frequency?
31.
The nuclei in a sample of a radioactive isotope decay by emitting α and γ particles. Which of the following is
correct for the energies of the α particles and for the energies of the γ particles?
[1 mark]
32.
A pure sample of a known element has a very long half-life. What measurement(s), together with the initial activity[1 mark]
of the sample, must be made in order to measure the half-life of the element?
A. The activity of the sample after a given period of time.
B. The mass of the sample after a given period of time.
C. The activity and the mass of the sample after a given period of time.
D. The mass of the sample.
This question is in two parts. Part 1 is about nuclear reactions. Part 2 is about thermal energy transfer.
Part 1 Nuclear reactions
33a.
(i) Define the term unified atomic mass unit.
(ii) The mass of a nucleus of einsteinium-255 is 255.09 u. Calculate the mass in
[2 marks]
MeVc–2.
33b.
When particle X collides with a stationary nucleus of calcium-40 (Ca-40), a nucleus of potassium (K-40) and a
proton are produced.
40 Ca
20
[6 marks]
1
+ X → 40
19 K+1 p
The following data are available for the reaction.
(i) Identify particle X.
(ii) Suggest why this reaction can only occur if the initial kinetic energy of particle X is greater than a minimum value.
(iii) Before the reaction occurs, particle X has kinetic energy 8.326 MeV. Determine the total combined kinetic energy of
the potassium nucleus and the proton.
33c.
Potassium-38 decays with a half-life of eight minutes.
[5 marks]
(i) Define the term radioactive half-life.
(ii) A sample of potassium-38 has an initial activity of 24×1012Bq. On the axes below, draw a graph to show the variation
with time of the activity of the sample.
(iii) Determine the activity of the sample after 2 hours.
Part 2 Thermal energy transfer
33d.
(i) Define the specific latent heat of fusion of a substance.
[5 marks]
(ii) Explain, in terms of the molecular model of matter, the relative magnitudes of the specific latent heat of vaporization
of water and the specific latent heat of fusion of water.
33e.
A piece of ice is placed into a beaker of water and melts completely.
The following data are available.
Initial mass of ice = 0.020 kg
Initial mass of water = 0.25 kg
Initial temperature of ice = 0°C
Initial temperature of water = 80°C
Specific latent heat of fusion of ice = 3.3×105J kg–1
Specific heat capacity of water = 4200 J kg–1K–1
(i) Determine the final temperature of the water.
(ii) State two assumptions that you made in your answer to part (f)(i).
[5 marks]
This question is about fundamental interactions.
The Feynman diagram shows the decay of a K+ meson into three other particles.
34a.
34b.
Identify particle A.
[1 mark]
(i) Identify the interaction whose exchange particle is represented by B.
(ii) Identify the exchange particle labelled C.
+
[2 marks]
34c.
Outline how the concept of strangeness applies to the decay of a K+ meson shown in this Feynman diagram.
[2 marks]
This question is about the standard model.
The Feynman diagrams show two electroweak interactions between electrons. The particle represented by the wavy
line is a photon.
35a.
State
[2 marks]
(i) the name of the exchange particle represented by the dotted line.
(ii) one difference between the two exchange particles.
35b.
36.
Outline how the observation of the interaction represented by the diagram with the dotted line provides
evidence for the standard model.
In a particular atom, the nucleon number is the total number of
A. protons.
B. neutrons.
C. electrons.
D. protons and neutrons.
[2 marks]
[1 mark]
37.
For which quantity can the unit MeVc–2 be used?
[1 mark]
A. Mass
B. Momentum
C. Kinetic energy
D. Binding energy
38. The nuclear reaction represented by
[1 mark]
1 n+235 U
0
92
92
1
→ 141
56 Ba+36 Kr + 30 n
is an example of
A. nuclear fusion.
B. nuclear fission.
C. artificial transmutation.
D. radioactive decay.
39. The diagram shows the three lowest energy levels of an atom.
Which diagram shows the emission line spectrum associated with electron transitions from energy level X?
[1 mark]
This question is in two parts. Part 1 is about electric fields and radioactive decay. Part 2 is about change of phase.
Part 1 Electric fields and radioactive decay
40a. Define electric field strength.
[2 marks]
–15
40b. A simple model of the proton is that of a sphere of radius 1.0×10 m with charge concentrated at the centre of [2 marks]
the sphere. Estimate the magnitude of the field strength at the surface of the proton.
6
–1
6
–1
40c. Protons travelling with a speed of 3.9×10 ms enter the region between two charged parallel plates X and Y.
Plate X is positively charged and plate Y is connected to earth.
[4 marks]
A uniform magnetic field also exists in the region between the plates. The direction of the field is such that the protons
pass between the plates without deflection.
(i) State the direction of the magnetic field.
(ii) The magnitude of the magnetic field strength is 2.3×10–4T. Determine the magnitude of the electric field strength
between the plates, stating an appropriate unit for your answer.
40d.
Protons can be produced by the bombardment of nitrogen-14 nuclei with alpha particles. The nuclear reaction
equation for this process is given below.
14 N + 4 He
7
2
→ X + 11 H
Identify the proton number and nucleon number for the nucleus X.
[1 mark]
40e. The following data are available for the reaction in (d).
[3 marks]
Rest mass of nitrogen-14 nucleus =14.0031 u
Rest mass of alpha particle =4.0026 u
Rest mass of X nucleus =16.9991 u
Rest mass of proton =1.0073 u
Show that the minimum kinetic energy that the alpha particle must have in order for the reaction to take place is about 0.7
Me V.
40f.
A nucleus of another isotope of the element X in (d) decays with a half-life
fluorine-19 (F-19).
T1
to a nucleus of an isotope of
[5 marks]
2
(i) Define the terms isotope and half-life.
(ii) Using the axes below, sketch a graph to show how the number of atoms N in a sample of X varies with time t, from t=0
to t = 3T 1 . There are N0 atoms in the sample at t=0.
2
Part 2 Change of phase
40g. Water at constant pressure boils at constant temperature. Outline, in terms of the energy of the molecules, the [2 marks]
reason for this.
40h.
In an experiment to measure the specific latent heat of vaporization of water, steam at 100°C was passed into
water in an insulated container. The following data are available.
[4 marks]
Initial mass of water in container = 0.300kg
Final mass of water in container = 0.312kg
Initial temperature of water in container = 15.2°C
Final temperature of water in container = 34.6°C
Specific heat capacity of water = 4.18×103Jkg–1K–1
Show that the data give a value of about 1.8×106Jkg–1 for the specific latent heat of vaporization L of water.
40i.
Explain why, other than measurement or calculation error, the accepted value of L is greater than that given in
(h).
[2 marks]
This question is in two parts. Part 1 is about simple harmonic motion (SHM) and waves. Part 2 is about atomic and
nuclear energy levels.
Part 1 Simple harmonic motion (SHM) and waves
41a.
A particle P moves with simple harmonic motion.
(i) State, with reference to the motion of P, what is meant by simple harmonic motion.
(ii) State the phase difference between the displacement and the velocity of P.
[3 marks]
Part 2 Atomic and nuclear energy levels
41b.
The diagram shows four spectral lines in the visible line emission spectrum of atomic hydrogen.
(i) Outline how such a spectrum may be obtained in the laboratory.
(ii) Explain how such spectra give evidence for the existence of discrete atomic energy levels.
[6 marks]
41c.
The energies of the principal energy levels in atomic hydrogen measured in eV are given by the expression
En =
[4 marks]
− 13.6
where n=1, 2, 3 ..........
n2
The visible lines in the spectrum correspond to electron transitions that end at n=2.
(i) Calculate the energy of the level corresponding to n=2.
(ii) Show that the spectral line of wavelength λ=485nm is the result of an electron transition from n=4.
The alpha particles and gamma rays produced in radioactive decay have discrete energy spectra. This suggests [2 marks]
that nuclei also possess discrete energy levels. However, beta particles produced in radioactive decay have continuous
energy spectra. Describe how the existence of the antineutrino accounts for the continuous nature of beta spectra.
41d.
This question is about particles.
+
0
42a. The Σ particle can decay into a π particle and another particle Y as shown in the Feynman diagram.
(i) Identify the exchange particle X.
(ii) Identify particle Y.
(iii) Outline the nature of the π0.
0
[4 marks]
42b.
The π0 particle can decay with the emission of two gamma rays, each one of which can subsequently produce
an electron and a positron.
[3 marks]
(i) State the process by which the electron and the positron are produced.
(ii) Sketch the Feynman diagram for the process in (c)(i).
+
42c. Discuss whether strangeness is conserved in the decay of the Σ particle in (a).
[1 mark]
43. An electron is accelerated through a potential difference of 100 V. Which of the following gives the correct gain in [1 mark]
kinetic energy of the electron in both joule and electronvolt?
238
44. A nucleus of the isotope plutonium-238 ( P) decays into a nucleus of uranium by emitting an alpha particle.
What is the nucleon number of the uranium nucleus?
[1 mark]
A. 234
B. 236
C. 238
D. 240
45. Which of the following affects the rate at which a sample of a radioactive material decays?
A. The mass of the sample
B. The temperature of the sample
C. The volume of the sample
D. The pressure acting on the sample
[1 mark]
46.
A fission reaction for uranium is
[1 mark]
235 U +
92
A
n → 141
56 Ba + Z Kr + 3n
where n is the neutron. Which of the following gives the value of the nucleon number A and proton number Z for the
krypton (Kr)?
This question is about conservation laws and the standard model.
−
−
47. A muon decays into an electron and two other particles according to the reaction equation μ →e +?+?.
State the names of the two other particles that are produced in this decay explaining your answer.
[3 marks]
This question is about linear accelerators.
48a.
A moving proton is incident on a stationary pion, producing a kaon (K meson) and an unknown hadron X
according to the reaction given below.
[2 marks]
p+π−→X+K−
(i) State, with a reason, the electric charge of X.
(ii) State, with a reason, if X is a baryon or a meson.
–18 N s are scattered by gold nuclei.
48b. In a deep inelastic scattering experiment, protons of momentum 2.70 ×10
[3 marks]
Given that the diameter of nucleons is of the order 10–15 m and the diameter of quarks is less than 10–18 m, determine if
these protons will be able to resolve
(i) nucleons within the gold nuclei.
(ii) quarks within the gold nuclei.
48c. Outline how deep inelastic scattering experiments led to the conclusion that gluons exist.
[2 marks]
This question is about the early universe and the Higgs boson.
The graph shows the variation of the logarithm of the temperature T of the universe with the logarithm of the time t
after the Big Bang.
49. Evidence for the Higgs boson might be discovered at the Large Hadron Collider (LHC) at CERN. Outline why such [2 marks]
a discovery would be of crucial significance to the standard model.
Part 2 Unified atomic mass unit and a nuclear reaction
50a.
50b.
Define the term unified atomic mass unit.
[1 mark]
The mass of a nucleus of rutherfordium-254 is 254.1001u. Calculate the mass in GeVc–2.
[1 mark]
50c.
In 1919, Rutherford produced the first artificial nuclear transmutation by bombarding nitrogen with α -particles. [4 marks]
The reaction is represented by the following equation.
17
α + 14
7 N→8 O+X
(i) Identify X.
(ii) The following data are available for the reaction.
Rest mass of α = 3.7428 GeVc–2
–2
Rest mass of 14
7 N = 13.0942 GeVc
–2
Rest mass of 17
8 O + X = 16.8383 GeVc
The initial kinetic energy of the α -particle is 7.68 MeV. Determine the sum of the kinetic energies of the oxygen nucleus
and X. (Assume that the nitrogen nucleus is stationary.)
50d. The reaction in (c) produces oxygen (O-17). Other isotopes of oxygen include O-19 which is radioactive with a
half-life of 30 s.
(i) State what is meant by the term isotopes.
(i) Define the term radioactive half-life.
[2 marks]
50e.
A nucleus of the isotope O-19 decays to a stable nucleus of fluorine. The half-life of O-19 is 30 s. At time t=0, a
sample of O-19 contains a large number N0 nuclei of O-19.
[2 marks]
On the grid below, draw a graph to show the variation with time t of the number N of O-19 nuclei remaining in the sample.
You should consider a time of t=0 to t=120s.
This question is about quarks.
The quark content of a π+ meson includes an up quark.
The Feynman diagram represents the decay of a π+ meson.
51a.
Identify the particles labelled A and B.
[2 marks]
51b. State, with reference to their properties, two differences between a photon and a W boson.
[2 marks]
This question is about strangeness.
52. The following particle interaction is proposed.
[2 marks]
p + π− → K − + π+
In this interaction, charge is conserved.
State, in terms of baryon and strangeness conservation, whether the interaction is possible.
This question is about radioactive decay.
Iodine-124 (I-124) is an unstable radioisotope with proton number 53. It undergoes beta plus decay to form an isotope
of tellurium (Te).
53a. State the reaction for the decay of the I-124 nuclide.
[2 marks]
53b.
The graph below shows how the activity of a sample of iodine-124 changes with time.
[6 marks]
(i) State the half-life of iodine-124.
(ii) Calculate the activity of the sample at 21 days.
(iii) A sample of an unknown radioisotope has a half-life twice that of iodine-124 and the same initial activity as the sample
of iodine-124. On the axes opposite, draw a graph to show how the activity of the sample would change with time. Label
this graph X.
(iv) A second sample of iodine-124 has half the initial activity as the original sample of iodine-124. On the axes opposite,
draw a graph to show how the activity of this sample would change with time. Label this graph Y.
This question is about mesons.
54a.
State what is meant by an exchange particle.
[1 mark]
A meson called the pion was detected in cosmic ray reactions in 1947 by Powell and Occhialini. The pion comes [2 marks]
in three possible charge states: π​+ ,​π− and ​π0. The Feynman diagram below represents a possible reaction in which a pion
participates.
54b.
State and explain whether the meson produced is a π​+ ,​π− or a ​π0.
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