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A2 · Topic 24

Physics that sees inside.

Ultrasound echoes and acoustic impedance, X-ray attenuation and contrast, and PET scanning built from positron annihilation. The physics of the imaging machines that look inside the body without opening it. Play the three simulations below. The gamified lessons and the topic Paper 4 practice are live below too.

Simulations · live
Interactive · live Ultrasound and acoustic impedance Set the impedances of two media and watch how much of the pulse echoes back at the boundary. Loads only when you launch, so the page stays fast.
Interactive · live X-ray attenuation Choose a material and thickness and watch the transmitted intensity fall as I = I₀e⁻μᵛ. Loads only when you launch, so the page stays fast.
Interactive · live PET scanning Watch positron annihilation send gamma pairs to the detector ring, building lines of response that cross at the tracer. Loads only when you launch, so the page stays fast.
Paper 4 practice · live
Structured questions · with worked solutions Ten original Paper 4 style questions A full topic set across ultrasound, X-rays and PET scanning, linking the lessons with full worked solutions. Open practice →
Lessons · live
Production and use of ultrasound → Production and use of X-rays → PET scanning →
Concept map
Open the concept map →