The mass defect for deuterium is 4×10^–30 kg. What is the binding energy of deuterium? 

A. 4×10^–7 eV 

B. 8×10^–2 eV 

C. 2×10⁶ eV 

D. 2×10¹² eV

C

As quarks separate from each other within a hadron, the interaction between them becomes larger. What is the nature of this interaction? 

A. Electrostatic
B. Gravitational 
C. Strong nuclear 
D. Weak nuclear

C

Two pulses are travelling towards each other.

What is a possible pulse shape when the pulses overlap?

A

What is the relation between the value of the unified atomic mass unit in grams and the value of Avogadro’s constant in mol⁻¹?

A. Their ratio is 1.

B. Their product is 1.

C. Their sum is 1.

D. Their difference is 0.

B

Photons of energy 2.3eV are incident on a low-pressure vapour. The energy levels of the atoms in the vapour are shown

What energy transition will occur when a photon is absorbed by the vapour? 

A. –3.9eV to –1.6eV

B. –1.6eV to 0eV 

C. –1.6eV to –3.9eV 

D. 0eV to –1.6eV

A

When an alpha particle collides with a nucleus of nitrogen-14 $\left({}_7^{14}\mathrm{N}\right)$, a nucleus X can be produced together with a proton. What is X?

A. ${}_8^{18}\mathrm{X}$

B. ${}_8^{17}\mathrm{X}$

C. ${}_9^{18}\mathrm{X}$

D. ${}_9^{17}\mathrm{X}$

B

The binding energy per nucleon of ${}_4^{11}Be$ is 6 MeV. What is the energy required to separate the nucleons of this nucleus?

A.  24 MeV

B.  42 MeV

C.  66 MeV

D.  90 MeV

C

In nuclear fission, a nucleus of element X absorbs a neutron (n) to give a nucleus of element Y and a nucleus of element Z.

X + n → Y + Z + 2n

What is $\frac{\text{magnitude of the binding energy per nucleon of Y}}{\text{magnitude of the binding energy per nucleon of X}}$ and $\frac{\text{total binding energy of Y and Z}}{\text{total binding energy of X}}$?

A

What is the energy equivalent to the mass of one proton?

A.  9.38 × (3 × 10⁸)² × 10⁶ J

B.  9.38 × (3 × 10⁸)² × 1.6 × 10^–19 J

C.  $\frac{9.38\times {10}^8}{1.6\times {10}^{-19}}$J

D.  9.38 × 10⁸ × 1.6 × 10^–19 J

D

A nucleus of phosphorus (P) decays to a nucleus of silicon (Si) with the emission of particle X and particle Y.

$${}_{15}^{30}\text{P}\to {}_{14}^{30}\text{Si}+\text{X}+\text{Y}$$

What are X and Y?

D

What statement about alpha particles, beta particles and gamma radiation is true?

A.  Gamma radiation always travels faster than beta particles in a vacuum.

B.  In air, beta particles produce more ions per unit length travelled than alpha particles.

C.  Alpha particles are always emitted when beta particles are emitted.

D.  Alpha particles are deflected in the same direction as beta particles in a magnetic field.

A

The Feynman diagram shows a particle interaction involving a W^– boson.

Which particles are interacting?

A. U and Y

B. W^– boson and Y

C. X and Y

D. U and X

C

The Feynman diagram shows some of the changes in a proton–proton collision.

What is the equation for this collision?

A.  $\mathrm{p}+\mathrm{p}\to \mathrm{p}+\mathrm{n}+{\mathrm{\pi }}^{+}$

B.  $\mathrm{p}+\mathrm{p}\to \mathrm{p}+\mathrm{n}+{\mathrm{\pi }}^{-}$

C.  $\mathrm{p}+\mathrm{p}\to \mathrm{p}+\overline{\mathrm{n}}+{\mathrm{\pi }}^{+}$

D.  $\mathrm{p}+\mathrm{p}\to \mathrm{p}+\overline{\mathrm{n}}+{\mathrm{\pi }}^{-}$

A

There were some teacher comments that this was not a complete Feynman diagram however the stem does say that the diagram shows some of the changes and is intended to make the question easier by not complicating with particles that do not change. Students should be made aware that they can expect to see diagrams like this in the future as partial diagrams do tend to make the situation simpler for students to solve.

Consider the Feynman diagram below.

What is the exchange particle X?

A. Lepton

B. Gluon

C. Meson

D. Photon

D

When a high-energy $\alpha$-particle collides with a beryllium-9 (${}_4{}^9\text{Be}$) nucleus, a nucleus of carbon $\left(\text{Z}=6\right)$ may be produced. What are the products of this reaction?

B

The half-life of a radioactive element is 5.0 days. A freshly-prepared sample contains 128 g of this element. After how many days will there be 16 g of this element left behind in the sample?

A. 5.0 days

B. 10 days

C. 15 days

D. 20 days

C

The energy-level diagram for an atom that has four energy states is shown.

What is the number of different wavelengths in the emission spectrum of this atom?

A.     1

B.     3

C.     6

D.     7

C

A simple model of an atom has three energy levels. The differences between adjacent energy levels are shown below.

What are the two smallest frequencies in the emission spectrum of this atom?

A.  0.5 × 10¹⁵Hz and 1.0 × 10¹⁵Hz

B.  0.5 × 10¹⁵Hz and 1.5 × 10¹⁵Hz

C.  1.0 × 10¹⁵Hz and 2.0 × 10¹⁵Hz

D.  1.0 × 10¹⁵Hz and 3.0 × 10¹⁵Hz

C

A graph of the variation of average binding energy per nucleon with nucleon number has a maximum. What is indicated by the region around the maximum?

A.     The position below which radioactive decay cannot occur

B.     The region in which fission is most likely to occur

C.     The position where the most stable nuclides are found

D.     The region in which fusion is most likely to occur

C

A proton collides with an electron. What are the possible products of the collision?

A.  Two neutrons

B.  Neutron and positron

C.  Neutron and antineutrino

D.  Neutron and neutrino

D

The mass of a nucleus of iron-56 (${}_{26}{}^{56}\text{Fe}$) is M.

What is the mass defect of the nucleus of iron-56?

A.  M − 26m_p − 56m_n

B.  26m_p + 30m_n − M

C.  M − 26m_p − 56m_n − 26m_e

D.  26m_p + 30m_n + 26m_e − M

B

Three particles are produced when the nuclide ${}_{12}{}^{23}\text{Mg}$ undergoes beta-plus (β⁺) decay. What are two of these particles?

A. ${}_{11}{}^{23}\text{Na}$ and ${}_0{}^0\text{v}_{\text{e}}$

B. ${}_{-1}{}^0\text{e}$ and ${}_0{}^0\text{v}_{\text{e}}$

C. ${}_{11}{}^{23}\text{Na}$ and ${}_0{}^0\overline{\text{v}}_{\text{e}}$

D. ${}_1{}^0\text{e}$ and ${}_0{}^0\overline{\text{v}}_{\text{e}}$

A

The diagram below shows four energy levels for the atoms of a gas. The diagram is drawn to scale. The wavelengths of the photons emitted by the energy transitions between levels are shown.

What are the wavelengths of spectral lines, emitted by the gas, in order of decreasing frequency?

A.  ${\lambda }_3, {\lambda }_2, {\lambda }_1, {\lambda }_4$

B.  ${\lambda }_4, {\lambda }_1, {\lambda }_2, {\lambda }_3$

C.  ${\lambda }_4, {\lambda }_3, {\lambda }_2, {\lambda }_1$

D.  ${\lambda }_4, {\lambda }_2, {\lambda }_1, {\lambda }_3$

B

Two pure samples of radioactive nuclides X and Y have the same initial number of atoms. The half-life of X is $T_{\frac{1}{2}}$.

After a time equal to 4 half-lives of X the ratio $\frac{\text{number of atoms of X}}{\text{number of atoms of Y}}$ is $\frac{1}{8}$.

What is the half-life of Y?

A.     $0.25T_{\frac{1}{2}}$

B.     $0.5T_{\frac{1}{2}}$

C.     $3T_{\frac{1}{2}}$

D.     $4T_{\frac{1}{2}}$

D

The graph shows the variation with time of the activity of a pure sample of a radioactive nuclide.

What percentage of the nuclide remains after 200 s?

A.   3.1 %

B.   6.3 %

C.   13 %

D.   25 %

B

${}_{92}{}^{238}\text{U}$ undergoes an alpha decay, followed by a beta-minus decay. What is the number of protons and neutrons in the resulting nuclide?

C

This question was generally well answered by candidates, however a significant number selected option A (incorrectly) perhaps due to confusion between nuclear mass and the number of neutrons. This question had a relatively high discrimination index.

The graph shows the variation of the number of neutrons N with the atomic number Z for stable nuclei. The same scale is used in the N and Z axes.

Which information can be inferred from the graph?

I.   For stable nuclei with high Z, N is larger than Z.

II.  For stable nuclei with small Z, N = Z.

III. All stable nuclei have more neutrons than protons.

A.   I and II only

B.   I and III only

C.   II and III only

D.   I, II and III

A

The following interaction is proposed between a proton and a pion.

p⁺ + $\pi$^– → K^– + $\pi$⁺

The quark content of the $\pi$^– is ūd and the quark content of the K^– is ūs.

Three conservation rules are considered

I.   baryon number

II.  charge

III. strangeness.

Which conservation rules are violated in this interaction?

A.   I and II only

B.   I and III only

C.   II and III only

D.   I, II and III

B

Copper (${}_{29}^{64}\text{Cu}$) decays to nickel (${}_{28}^{64}\text{Ni}$). What are the particles emitted and the particle that mediates the interaction?

D

Which Feynman diagram shows the emission of a photon by a charged antiparticle?

C

Which of the following atomic energy level transitions corresponds to photons of the shortest wavelength?

C

The most common (incorrect) response was A, where students apparently assumed energy difference was proportional to the wavelength of the emitted photon.

Four of the energy states for an atom are shown. Transition between any two states is possible.

What is the shortest wavelength of radiation that can be emitted from these four states?

A.  $\frac{hc}{E_4-E_1}$

B.  $\frac{hc}{E_4}-\frac{hc}{E_1}$

C.  $\frac{hc}{E_4-E_3}$

D.  $\frac{hc}{E_4}-\frac{hc}{E_3}$ 

A

Three statements about radioactive decay are:

I.   The rate of decay is exponential.
II.  It is unaffected by temperature and pressure.
III. The decay of individual nuclei cannot be predicted.

Which statements are correct?

A.  I and II only

B.  I and III only

C.  II and III only

D.  I, II and III

D

Option B was the most frequent answer by candidates, suggesting that many candidates are unclear about the basic characteristics of radioactive decay.

Which statement about atomic spectra is not true?

A. They provide evidence for discrete energy levels in atoms.

B. Emission and absorption lines of equal frequency correspond to transitions between the same two energy levels.

C. Absorption lines arise when electrons gain energy.

D. Emission lines always correspond to the visible part of the electromagnetic spectrum.

D

Three statements about electrons are:

I.   Electrons interact through virtual photons.
II.  Electrons interact through gluons.
III. Electrons interact through particles W and Z.

Which statements identify the particles mediating the forces experienced by electrons?

A. I and II only

B. I and III only

C. II and III only

D. I, II and III

B

What is the definition of the unified atomic mass unit?

A.  $\frac{1}{12}$ the mass of a neutral atom of carbon-12

B.  The mass of a neutral atom of hydrogen-1

C.  $\frac{1}{12}$ the mass of a nucleus of carbon-12

D.  The mass of a nucleus of hydrogen-1

A

A particle reaction is

$p+e^{-}+{\overline{V}}_{\mu }\to n+{\mu }^{+}+v_e$.

Which conservation law is violated by the reaction?

A. Baryon number

B. Charge

C. Lepton number

D. Momentum

B

The age of the Earth is about 4.5 × 10⁹ years.

What area of physics provides experimental evidence for this conclusion?

A.  Newtonian mechanics

B.  Optics

C.  Radioactivity

D.  Electromagnetism

C

Which property of a nuclide does not change as a result of beta decay?

A. Nucleon number

B. Neutron number

C. Proton number

D. Charge

A

Response A was the most common (correct) response from a minority of candidates (38 %). Incorrect responses were evenly divided among the remaining options.

A radioactive nuclide with atomic number Z undergoes a process of beta-plus (β⁺) decay. What is the atomic number for the nuclide produced and what is another particle emitted during the decay?

A

Element X decays through a series of alpha (α) and beta minus (β^–) emissions. Which series of emissions results in an isotope of X?

A.     1α and 2β^–

B.     1α and 4β^–

C.     2α and 2β^–

D.     2α and 3β^–

A

Which Feynman diagram shows beta-plus (β⁺) decay?

A

Three of the fundamental forces between particles are

          I.     strong nuclear

          II.     weak nuclear

          III.     electromagnetic.

What forces are experienced by an electron?

A.     I and II only

B.     I and III only

C.     II and III only

D.     I, II and III

C

A pure sample of radioactive nuclide $\text{X}$ decays into a stable nuclide $\text{Y}$.

What is $\frac{\text{number of atoms of Y}}{\text{number of atoms of X}}$ after two half-lives?

A.  1

B.  2

C.  3

D.  4

C

The reaction p⁺ + n⁰ → p⁺ + $\pi$⁰ does not occur because it violates the conservation law of

A.  electric charge.

B.  baryon number.

C.  lepton number.

D.  strangeness.

B

Which graph shows the variation of activity $A$ with time $t$ for a radioactive nuclide?

D

The energy levels for an atom are shown to scale.

A photon of wavelength λ is emitted because of a transition from E₃ to E₂. Which transition leads to the emission of a photon of longer wavelength?

A. E₄ to E₁

B. E₄ to E₃

C. E₃ to E₁

D. E2 to E₁

B

The average binding energy per nucleon of the ${}_8^{15}\text{O}$ nucleus is 7.5 MeV. What is the total energy required to separate the nucleons of one nucleus of ${}_8^{15}\text{O}$?

A.     53 MeV

B.     60 MeV

C.     113 MeV

D.     173 MeV

C

Three conservation laws in nuclear reactions are

I. conservation of charge

II. conservation of baryon number

III. conservation of lepton number.

The reaction

$n\to {\pi }^{-}+e^{+}+{\overline{v}}_e$

is proposed.

Which conservation laws are violated in the proposed reaction?

A. I and II only

B. I and III only

C. II and III only

D. I, II and III

C

Atomic spectra are caused when a certain particle makes transitions between energy levels.
What is this particle?

A. Electron

B. Proton

C. Neutron

D. Alpha particle

A

X is a radioactive nuclide that decays to a stable nuclide. The activity of X falls to $\frac{1}{16}$th of its original value in 32 s.
What is the half-life of X?

A.  2 s

B.  4 s

C.  8 s

D.  16 s

C

A proton, an electron and an alpha particle are at rest. Which particle has the smallest magnitude of ratio of charge to mass and which particle has the largest magnitude of ratio of charge to mass?

A

What is correct about the nature and range of the strong interaction between nuclear particles?

A. It is attractive at all particle separations.

B. It is attractive for particle separations between 0.7 fm and 3 fm.

C. It is repulsive for particle separations greater than 3 fm.

D. It is repulsive at all particle separations.

B

The energy levels of an atom are shown. How many photons of energy greater than 1.9 eV can be emitted by this atom?

A.  1

B.  2

C.  3

D.  4

D

The background count in a laboratory is 20 counts per second. The initial observed count rate of a pure sample of nitrogen-13 in this laboratory is 180 counts per second. The half-life of nitrogen-13 is 10 minutes. What is the expected count rate of the sample after 30 minutes?

A.  20 counts per second

B.  23 counts per second

C.  40 counts per second

D.  60 counts per second

C

Option B was the most frequent answer, incorrectly selected by candidates who did not consider the background count in the laboratory.

A kaon is made up of two quarks. What is the particle classification of a kaon?

A. Exchange boson

B. Baryon

C. Lepton

D. Meson

D

The positions of stable nuclei are plotted by neutron number n and proton number p. The graph indicates a dotted line for which n = p. Which graph shows the line of stable nuclides and the shaded region where unstable nuclei emit beta minus (β^-) particles?

D

This question proved challenging, a low discrimination index and a relatively even spread of answers suggests that maybe guesswork was responsible for the candidates choice.

The rest mass of the helium isotope ${}_2^3\text{He}$ is m.

Which expression gives the binding energy per nucleon for ${}_2^3\text{He}$?

A. $\frac{(2m_p+m_n+m)c^2}{3}$

B. $\frac{(2m_p+m_n-m)c^2}{3}$

C. $(2m_p+m_n+m)c^2$

D. $(2m_p+m_n-m)c^2$

B

What gives the total change in nuclear mass and the change in nuclear binding energy as a result of a nuclear fusion reaction?

B

Some transitions between the energy states of a particular atom are shown.

Energy transition E₃ gives rise to a photon of green light. Which transition will give rise to a photon of longer wavelength?

A.  E₁

B.  E₂

C.  E₄

D.  E₅

C

This question was well answered by SL candidates, although answer A was a distractor for many. This question had the highest discrimination index on this SL paper.

The Higgs boson was discovered in the Large Hadron Collider at CERN. Which statements are correct about the discovery of the Higgs boson?

I.   It was independent of previous theoretical work.
II.  It involved analysing large amounts of experimental data.
III. It was consistent with the standard model of particle physics.

A.  I and II only

B.  I and III only

C.  II and III only

D.  I, II and III

C

What statement is not true about radioactive decay?

A.  The percentage of radioactive nuclei of an isotope in a sample of that isotope after 7 half-lives is smaller than 1 %.

B.  The half-life of a radioactive isotope is the time taken for half the nuclei in a sample of that isotope to decay.

C.  The whole-life of a radioactive isotope is the time taken for all the nuclei in a sample of that isotope to decay.

D.  The half-life of radioactive isotopes range between extremely short intervals to thousands of millions of years.

C

There was some questioning about the use of the term 'whole-life' from teacher comments. As that option (C) was the correct answer and the most popular it did not confuse the candidates. The statement is clearly incorrect and the use of a non physics specific term that might be used in a general discussion was felt to be acceptable.

A detector, placed close to a radioactive source, detects an activity of 260 Bq. The average background activity at this location is 20 Bq. The radioactive nuclide has a half-life of 9 hours.

What activity is detected after 36 hours?

A.     15 Bq

B.     16 Bq

C.     20 Bq

D.     35 Bq

D