# Doctors use ultrasound waves to carry out foetal scanning. Explain how ultrasound waves are used to produce an image of a foetus inside the womb.

> Eduqas A-Level Physics — 5.3 Electric and magnetic fields (A-Level only) · Explain · 5 marks

> Ultrasound scanning is a routine procedure used during pregnancy. The scanner is placed against the surface of the mother's skin and an image appears on a screen within seconds.

## Mark scheme (5 marks)

1. Ultrasound waves are emitted from the scanner into the body
2. Ultrasound waves have a frequency higher than the upper limit of human hearing (above 20 kHz)
3. The ultrasound waves are reflected at boundaries between different tissues / at the surface of the foetus
4. The reflected waves are detected by the scanner
5. The time taken for the waves to return is used to determine the position / distance of the foetus, and a computer builds up an image

## Key terms

- [ultrasound waves](https://www.gradenine.co.uk/glossary/ultrasound-waves)
- [foetal scanning](https://www.gradenine.co.uk/glossary/foetal-scanning)

## Related

- [Revision notes for Eduqas A-Level Physics](https://www.gradenine.co.uk/learn)
- [How to answer "Explain" questions](https://www.gradenine.co.uk/tools/command-word-cheatsheet)
- [Practice this with AI marking (free)](https://www.gradenine.co.uk/start)

---
Source: [GradeNine](https://www.gradenine.co.uk/q/doctors-use-ultrasound-waves-to-carry-77cfbef7) · Published by Druglandscape Ltd.