Reflection, refraction, and sound waves - OCR GatewayUltrasound

Ultrasound is sound with a frequency greater than 20,000 Hz. Humans cannot hear ultrasound but many other animals can, such as mice, dogs and porpoises.

Ultrasound is useful because it has a short wavelength so it can be focussed into a beam.

Uses of ultrasound - Higher

Ultrasound scans are used to form images of things inside the body, such as an unborn baby. This is due to the fact that ultrasound can be transmitted through soft tissue, but is mostly reflected when it comes into contact with more dense material such as bone. Any ultrasound that is not reflected will be absorbed by the body. Doctors also use ultrasound to monitor blood flow and destroy kidney stones.

Sonar - Higher

Sonar equipment is used by ships and submarines to determine the depth of a sea floor bed or the position of shoals of fish. A signal is sent out from a transmitter and the reflected signal (the echo) is then detected back on the ship. If the time and speed are known then the distance to the position of the object that reflects the sound can be calculated using:

distance (m) = speed of sound in water (m/s) × time taken (s)

This is when:

• distance is measured in metres (m)
• speed of sound in water is measured in metres per second (m/s)
• time taken is measured in seconds (s)