2025 · Paper 2 · Physics
Question 10
The printed question, the official key, and each model’s JSON answer plus the reasoning it wrote.
PhysicsPaper 2Numerical
Q10
Official 11.7 – 11.9
Model answers
Claude Fable 5.1
Anthropic
Correct4 / 4
11.8
Claude Fable 5.1 reasoning
Photon 1: hν₁ = 13.6 + 10 = 23.6 eV (ignoring recoil of the proton, as intended). Positronium ground state energy: with reduced mass m/2, E = −13.6/2 = −6.8 eV. Energy conservation for electron (10 eV) + positron (at rest) → positronium (KE 5 eV, binding −6.8 eV) + photon: 10 = 5 − 6.8 + hν₂ ⇒ hν₂ = 11.8 eV. Difference: 23.6 − 11.8 = 11.8 eV.
GPT 6 Astra
OpenAI
Correct4 / 4
11.8
GPT 6 Astra reasoning
No written reasoning was returned for this item.
GPT 5.6 Luna
OpenAI
Correct4 / 4
11.8
GPT 5.6 Luna reasoning
No written reasoning was returned for this item.