Putting the return to work
A ship sends a sound pulse down into the sea. A pulse is a short burst of sound. The pulse comes back from the seabed, the sea floor.
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Rule
Sonar times an echo to find a distance under water. The pulse goes there and back. So the distance is half of speed × time.
- Sonar — timing an ultrasound echo to find distance under water.
- Echolocation — an animal finding things by their echoes, as bats do.
A pulse returns after 3 s. Sound in seawater travels at about 1500 m/s. There and back = 1500 × 3 = 4500 m. The round trip is down and up, so divide by 2. Depth = 4500 ÷ 2 = 2250 m.
| Who | What the echo shows |
|---|---|
| A bat | Where an insect is |
| A ship | How deep the sea is |
| A doctor | Organs, or a baby before birth |
| An engineer | A crack hidden inside metal |