Special relativity exam tips

Exam tips

• Calculate the Lorentz factor before comparing lengths

  Compute γ = 1/√(1‑v²/c²) and use it to find the contracted length, then compare with the optical length.

  Define both: length contraction is the real shortening of a moving object's proper length; optical appearance is the apparent shift due to light travel time. Identify key difference: contraction is calculated from the Lorentz factor and is independent of light propagation; optical appearance depends on the observer’s position and the time light takes to travel. Explain when each applies: use the Lorentz factor when you need the true length in the observer’s frame; use optical appearance when the question involves the time it takes for light to reach the observer from the rod’s ends. Conclude: performing the calculation first ensures you apply the correct concept and avoid mixing the two.

• Use the graph feature in Length contraction

  Use the graph feature first, then connect it to Distinguish length contraction from optical appearance. using one named experiment, one observation and one physics conclusion.

  Turning Points answers need evidence-based reasoning: method, observation, conclusion and why the older model is limited.

• State the model change in Length contraction

  State the model change first, then connect it to Distinguish length contraction from optical appearance. using one named experiment, one observation and one physics conclusion.

  Turning Points answers need evidence-based reasoning: method, observation, conclusion and why the older model is limited.

• Model comparison method

  Compare classical and modern models by naming the failed prediction, the observed result and the replacement explanation.

  This wording forces an evidence-observation-conclusion chain, which is the safest structure for AQA A-level Physics Turning Points questions.