Medical physics

Medical physics is a fascinating branch of physics that applies physical principles to medicine, particularly in imaging and treatment. In AQA A-Level Physics, this topic covers how X-rays, ultrasound, and radionuclides are used to diagnose and treat diseases. You'll explore the physics behind CT scans, PET scans, and radiotherapy, linking concepts like attenuation, half-life, and the photoelectric effect to real-world medical applications. Understanding medical physics not only deepens your grasp of waves, radiation, and nuclear physics but also shows how physics saves lives—making it a highly rewarding topic for exams and beyond.

This topic is part of the 'Option' section of the AQA A-Level Physics specification (Option A: Astrophysics, Option B: Medical physics, etc.). It builds on core knowledge from Waves, Particles and Radiation, and Nuclear Physics. You'll need to recall equations for exponential decay, intensity, and attenuation, and apply them to clinical scenarios. Medical physics questions often appear in Paper 3 (Section B), where you'll analyse data, interpret images, and evaluate risks and benefits. Mastery of this topic demonstrates your ability to connect abstract physics to practical, high-stakes applications—a skill examiners love.

Why does medical physics matter? It's the science behind every X-ray, MRI scan, and cancer treatment. By studying it, you'll understand how doctors see inside the body without surgery, how they target tumours with minimal damage to healthy tissue, and how they ensure patient safety. This topic also introduces ethical considerations, such as radiation dose limits and the ALARP principle (As Low As Reasonably Practicable). For your revision, focus on the mechanisms of image formation, the factors affecting image quality, and the calculations involving half-life and attenuation coefficients. These are the areas where students gain—or lose—marks.