The AQA A-level Physics Paper 3B (June 2022), Option D (Turning Points in Physics), explores foundational experiments and theoretical developments. Topics include Newton’s and Huygens’ theories of light, Grimaldi’s diffraction experiments, and Millikan’s oil drop experiment for determining electron charge. The paper also addresses Fizeau’s method for measuring the speed of light, the significance of Maxwell’s equations, and relativistic effects on mass and energy. Students analyze kinetic energy-speed relationships and explore implications of Einstein’s theory of relativity. Keywords: AQA Physics, turning points, light theories, Millikan, Fizeau, Maxwell, relativity, diffraction.