The Physics Question Bank

Specification: AQA A-level Physics (7408) 3.12 Turning points in physics option  |  Paper: 3 Section B  |  Data and formulae booklet: given in the exam

Every equation in the Turning points option has its own page: key definitions, the equation with units, and 10 ramped questions from core to stretch, each with a full worked solution.

🛒 All the equations in one place: the AQA A-level Every Key Equation PowerPoint has 127 equations, 381 practice questions and 15 derivations for £12.

The discovery of the electron (3.12.1)

• Electron gun: ½mv² = eV (3.12.1.2)
• Specific charge of the electron: e/m (3.12.1.3)
• Millikan’s oil drop: QV/d = mg (3.12.1.4)
• Stokes’ law: F = 6πηrv (3.12.1.4)

Wave–particle duality (3.12.2)

• Speed of electromagnetic waves: c = 1/√(μ₀ε₀) (3.12.2.3)
• Electron wavelength: λ = h/√(2meV) (3.12.2.5)

Special relativity (3.12.3)

• Time dilation: t = t₀/√(1 − v²/c²) (3.12.3.3)
• Length contraction: l = l₀√(1 − v²/c²) (3.12.3.4)
• Mass and energy: E = mc² = m₀c²/√(1 − v²/c²) (3.12.3.5)

How to use these pages: work every question on paper first. Convert eV and MeV to joules before using SI equations, decide which observer measures the proper time or proper length before you substitute, and keep v/c to at least 3 significant figures in relativity questions.

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