Uses of Sound Waves: Ultrasound Waves
Physics: AQA GCSE Higher, topic 6.3.6
Ultrasound Waves
When ultrasound waves meet a boundary between two different materials, some are reflected. We can work out how far away a boundary is based on how long it takes for reflections to reach a detector. We can use ultrasound waves for both medical and industrial imaging.
Medicine
- Doctors use ultrasound to perform scans of a developing foetus.
- Ultrasound waves can pass through the body.
- Whenever they reach a boundary between two different materials, some will be reflected. We can detect the reflected waves.
- A computer processes the timing and distribution of these waves. The computer uses these to produce a video image of the foetus.
Industry
- We can use ultrasound to find flaws in objects or materials (e.g. pipes or wood).
- When ultrasound waves enter a material, they will normally be reflected by the far side of the material.
- If there is a flaw (e.g. a crack), the waves will be reflected sooner. This tells us that there is a problem.
Water depth
- We can use echo sounding to detect objects in deep water and also to measure water depth.
- We send an ultrasound pulse into the water. When this pulse hits any surface, it is reflected back.
- We can work out the distance travelled by the sound wave by recording the time between us sending the pulse and detecting the reflection.
Training dogs
- Ultrasound has a frequency above 20,000Hz. Humans cannot hear sounds with frequencies this high, but other animals can.
- Dog whistles have frequencies above 20,000Hz. This is why humans cannot hear them.
Test yourself on Uses of Sound Waves: Ultrasound Waves
Which of these is not a use of ultrasound?
Measuring Water Depth