Waves for detection and exploration (physics only) (HT only) — AQA GCSE Physics
Test yourself on Waves for detection and exploration (physics only) (HT only) with AQA GCSE practice questions.
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Waves for detection and exploration (physics only) (HT only) explained
This is the big idea of the section, Higher tier physics only.
Read the full explanation
We cannot see inside a body, a weld or the Earth, so we send a wave in and read what comes back. Three properties do the work. Velocity: a wave changes speed when the material changes, which refracts it and alters the travel time. Absorption: materials soak up some waves more than others, so dense bone or a flaw in a casting shows up as a shadow. Reflection: at every boundary part of the wave is reflected, and the time it takes to return gives the depth of that boundary. Ultrasound scanning uses partial reflection at soft tissue boundaries, X-ray imaging uses differences in absorption, and seismology uses differences in velocity together with the fact that S-waves stop at a liquid.
Your focus
- Explain how the time for a reflected pulse to return reveals the depth of a hidden boundary.
- Compare the way ultrasound and X-rays produce a medical image, naming the property each depends on.
- Suggest, for a given hidden structure, which wave property would allow it to be detected and why.
Waves for detection and exploration (physics only) (HT only) exam tips
Marking Points
- one mark for stating that part of the wave is reflected at each boundary between two different materials
- one mark for linking the time for a reflection to return to the depth of that boundary
- one mark for saying that the wave speed differs between materials, so the wave refracts or takes a different time
- one mark for using a difference in absorption to explain why one structure shows up against another
Examiner Tips
- 💡Decide first which of the three properties the context depends on, then build the answer around it.
- 💡For any how do we know what is inside question, start with the boundary and what happens there.
- 💡Use qualitative comparisons carefully: faster, slower, more strongly absorbed, partially reflected.
Common Mistakes
- saying the wave passes through and shows the shape, with no mention of reflection or absorption
- using ultrasound and X-rays interchangeably, when one relies on reflection and the other on absorption
- forgetting that only part of the wave is reflected, so the rest continues to deeper boundaries
- describing a detector as producing the image without the return signal being timed or measured