AQA A-Level Physics Paper 1, June 2024: Question 1

Mark scheme

Show the mark scheme

Question Answers Additional comments/Guidelines Mark AO

01.1 gravity, weak (nuclear), strong (nuclear), electromagnetic Any order, all four must be correct. 1 AO1

Condone any reference to “interaction” or

“force”

Condone “gravitational”

Do not accept ‘electrostatic’, ‘gravitational

potential’, ‘em’, ‘EM’

01.2 proton, beta minus, (electron) antineutrino all correct Allow alternative ways of writing beta minus: 1 AO1

electron/ e / e- / β-

Accept p and P for proton and υ�e or υ� for

antineutrino

Condone ‘anti electron neutrino’

01.3 weak (nuclear) 2 AO1

Accept reference to W- or W together with

it involves leptons

(which do not experience strong interaction/force) transfer of charge (from neutron)

OR Accept d (quark) converted to u (quark)

there is a change in quark (flavour)

MP2 is conditional on award of MP1

01.4 idea that the exchange particle is a (virtual) photon 3 AO1

(virtual) photons/the exchange particles have momentum

Accept γ for photon.

conservation of momentum (means that photon

interchange) enables the electron momentum/path to

change

Total 7

How to answer it

Fundamental Particles and Interactions

What this question tests

This question assesses your core knowledge of particle physics, specifically recalling the four fundamental interactions, neutron decay products and mechanisms, and explaining electrostatic repulsion using virtual exchange particles (virtual photons) and conservation of momentum.

Question 01.1 [1 mark]

State the names of the four fundamental interactions.

✅ Correct Answer

Any order of: Gravity, Weak (nuclear), Strong (nuclear), Electromagnetic

💡 Key Knowledge

You must commit all four fundamental forces to memory. Examiners accept terms like "gravitational", "weak interaction", or "strong force".

❌ Common Errors

Writing shorthand like EM , em , "electrostatic", or "gravitational potential" will lose you the mark.

Mark scheme note: All four must be correct for the 1 mark. Condone the word "force" instead of "interaction".

Question 01.2 [1 mark]

State the products of the decay of a free neutron.

✅ Correct Answer

Proton, beta-minus (electron), (electron) antineutrino (all three required)

💡 Key Knowledge

Free neutron decay equation: n → p + e⁻ + ν̄ₑ . Memorise the components of beta-minus decay.

❌ Common Errors

Forgetting to include the antineutrino or incorrectly writing a neutrino instead of an antineutrino results in zero marks.

Mark scheme note: Alternative acceptable notations include p , e⁻ or β⁻ , and ν̄ₑ or ν̄ .

Question 01.3 [2 marks]

Explain which of the fundamental interactions is responsible for the decay of the neutron.

✅ Correct Answer

Weak (nuclear) interaction [1 mark]
Reason: It involves leptons (which do not experience the strong force) OR there is a change in quark flavour (down quark changes to up quark via W⁻ boson) [1 mark]

🧠 Exam Technique

This is a two-part requirement question ("State and Explain"). Mark point 2 (MP2) is conditional on successfully awarding Mark point 1 (MP1).

❌ Common Errors

Vague statements like "because it breaks down" or referencing the strong nuclear force will fail to gain credit.

Examiner insight: Top-level responses explicitly linked the interaction to quark flavour change (d → u) or lepton involvement.

Question 01.4 [3 marks]

The forces between two moving electrons cause their paths to change. Explain, using the concept of exchange particles, why the electron paths change.

✅ Correct Answer

The exchange particle is a (virtual) photon ( γ ) [1 mark].
(Virtual) photons / exchange particles carry momentum [1 mark].
Conservation of momentum (due to photon emission/absorption) enables the electron momentum/path to change [1 mark].

💡 Key Knowledge

For electromagnetic interactions between charged particles, the exchange particle is always a virtual photon. Force is fundamentally a consequence of momentum transfer during exchange.

❌ Common Errors

Students often talk about "charges repelling" without mentioning exchange particles, momentum, or virtual photons, missing all 3 marks.

Mark scheme note: Must explicitly reference momentum transfer and virtual photons to secure full marks.

Topics

Physics · 3.2 Particles and radiation