2.  Some animals such as bats, use ultrasound waves to detect obstacles and objects around them.  Ultrasounds are reflected of surfaces or objects and animals can listen to the echoes.

3.  We can use a similar method to detect things we cannot see using ultrasound.  Ships use sonar equipment to find the depth of the sea or to detect fish.

4.  Ultrasound can be used to make images of things inside the body.  One common use is to make images of unborn babies to see how the foetus is developing.

6.  Distance can be calculated by using the following equation: distance (m) = speed (m/s) x time (s)

7.  A ship detects a sonar pulse 3 seconds after it was emitted. The speed of sound in the sea water is 1500 m/s. 1. How far has the sound travelled? 2. How deep is the water?

8.  4500m  2250m