AQA A-Level Physics Paper 1, June 2022: Question 13

1 mark · Medium difficulty · Multiple Choice

Identify which combination of quarks is possible from the given options.

Practise this question

Question

Multiple choice question 13 asking 'Which combination of quarks is possible?' worth 1 mark. The options are A: sd, B: su-bar, C: su-bar d, D: ud, each with a corresponding answer box next to it.
Question text

13 Which combination of quarks is possible?

[1 mark]

A sd

B sū

C sūd

D ud

Mark scheme

Show the mark scheme Mark scheme showing that question 13 has the correct answer B (AO2), corresponding to su-bar.

13 B (AO2) sū

How to answer it

Determining Possible Quark Combinations

What this question tests

This question assesses your knowledge of particle physics, specifically classifying hadrons (mesons vs baryons) and understanding the allowed quark-antiquark pairings that form real mesons based on fundamental composition rules.

Question 1.3

Which combination of quarks is possible?

✅ Correct Answer: Option B (sü)

This is a valid meson consisting of a strange quark ( s ) and an up antiquark ( ū ). It corresponds to a K⁻ meson (kaon).

💡 Key Knowledge

  • Mesons are hadrons composed of exactly one quark and one antiquark.
  • Baryons are hadrons composed of three quarks (or three antiquarks).
  • Every quark has a corresponding antiquark with opposite charge, baryon number, and strangeness.

🧠 Exam Technique

Count the number of items and check their types (quark vs antiquark). Look for a combination of one quark and one antiquark to find a meson. If it has two quarks (like options A and D) or three quarks (like option C), immediately eliminate it if it doesn't fit standard hadron classes.

❌ Common Errors

  • Assuming any two quarks can pair up to form a stable or possible particle (forgetting hadrons must be colour-neutral and follow strict baryon/meson structures).
  • Confusing quarks ( u , d , s ) with antiquarks ( ū , d̄ , s̄ ). Option C ( sūd ) has three constituents, but contains two quarks and one antiquark—which does not form a standard baryon or meson!
Mark Breakdown: 1 mark available for selecting option B ( sü ).

Topics

Physics · 3.2 Particles and radiation

Question and mark scheme from the AQA A-Level Physics examination, Paper 1, June 2022. QuestionVault is an independent revision resource; questions remain the copyright of the awarding body.