2025 · Paper 1 · Physics
Question 9
The printed question, the official key, and each model’s JSON answer plus the reasoning it wrote.
PhysicsPaper 1Numerical
Q09
Official 21 – 25
Model answers
Claude Fable 5.1
Anthropic
Correct4 / 4
23
Claude Fable 5.1 reasoning
Energy density: u = N h f / V = 35×10⁷ × 6×10⁻³⁴ × 10¹⁵ = 21×10⁻¹¹ = 2.1×10⁻¹⁰ J/m³. Average energy density of EM wave: u = B₀²/(2μ₀). B₀² = 2μ₀u = 2 × 4π×10⁻⁷ × 2.1×10⁻¹⁰ = 8 × (22/7) × 2.1 × 10⁻¹⁷ = 8 × 6.6 × 10⁻¹⁷ = 52.8×10⁻¹⁷ = 5.28×10⁻¹⁶ B₀ = √5.28 × 10⁻⁸ ≈ 2.298×10⁻⁸ T ≈ 23 × 10⁻⁹ T. So α ≈ 23.
GPT 6 Astra
OpenAI
Correct4 / 4
22.98
GPT 6 Astra reasoning
No written reasoning was returned for this item.
GPT 5.6 Luna
OpenAI
Correct4 / 4
23
GPT 5.6 Luna reasoning
No written reasoning was returned for this item.