Ultrasound

Intermediate

Sound above 20 kHz used in imaging and cleaning.

Sound above 20 kHz used in medical imaging (1–15 MHz), cleaning, and sonar. Imaging uses echoes of short pulses from tissue boundaries.

Worked example

Foetal scanning.

Common mistake

Higher frequency gives finer detail but less penetration.

In more detail

Ultrasound is sound above 20 kHz, which is used for imaging and cleaning because it can be directed and has short wavelengths.

Medical ultrasound images the foetus, organs and blood flow.
Ultrasonic cleaners remove dirt from jewellery and instruments.
Medical ultrasound scanners use sound above 20 kHz to create images of the body without radiation.

Is ultrasound harmful?

At diagnostic levels it is considered safe for most uses.

Why is it used for imaging?

Short wavelengths give fine detail, and reflections reveal boundaries between tissues.

Why is ultrasound useful for imaging?

Short-wavelength sound reflects from small structures and boundaries, so it gives detailed images in soft tissue.