AQA AS Level Physics Paper 2, June 2022: Question 9

1 mark · Medium difficulty · Multiple Choice

Identify the correct row matching a particle name with its classification and quark structure.

Practise this question

Question

Multiple choice question 09 asking which row in a table is correct, worth 1 mark. The table has columns for Name of particle, Classification, and Quark structure, with rows A through D containing various particles such as antineutron, positive kaon, antiproton, and positive pion.
Question text

09 Which row is correct?

[1 mark]

Name of particle Classification Quark structure

A antineutron meson u u d

B positive kaon baryon u s

C antiproton baryon u u d

D positive pion meson u d

Mark scheme

Show the mark scheme Mark scheme indicating the correct answer is C, corresponding to antiproton, baryon, with quark structure u-bar u-bar d-bar.

09 C (AO1) antiproton baryon uu d

How to answer it

Particle Classifications and Quark Structures

What this question tests

This question assesses your core knowledge of particle physics (AQA AS Level Particles topic). Specifically, it tests your ability to link a particle's name and classification (baryon vs. meson) with its correct constituent quark-antiquark or three-quark structure, keeping close track of matter and antimatter quark rules.

Question 09

Multiple Choice Analysis

✅ Correct Answer: C

Row C is the correct choice. An antiproton is a baryon composed of three antiquarks ( ūūd̄ ).

1 mark available (AO1)

💡 Key Knowledge

  • Baryons are hadrons made of 3 quarks (or antibaryons made of 3 antiquarks). Protons are uud , so antiprotons must be made of three antiquarks: ūūd̄ .
  • Mesons are hadrons made of a quark-antiquark pair.
  • Antiparticles of quarks are denoted with a bar overhead (e.g., ū is an anti-up quark).

🧠 Exam Technique

Process of elimination is your best tool for multiple-choice particle rows:

  • Check the classification column first (e.g., baryons must have 3 quarks/antiquarks; mesons must have 2).
  • Immediately discard rows where classification and quark structure mismatch (e.g., calling a baryon a meson or giving a meson 3 quarks).

❌ Common Errors

  • Confusing particles and antiparticles: Assuming an antiproton has normal quark composition or mixing up up and down antiquarks. Remember that the antiproton is the antimatter counterpart to a proton ( uud ), so all its constituent quarks change to antiquarks ( ūūd̄ ).
  • Mixing up hadron groups: Confusing the particle family definitions—remembering that mesons have 2 quarks (quark-antiquark) while baryons have 3.

Topics

Physics · 3.2 Particles and radiation

Question and mark scheme from the AQA AS Level Physics examination, Paper 2, June 2022. QuestionVault is an independent revision resource; questions remain the copyright of the awarding body.