A ship sends a pulse of ultrasound down…

Contributed by StemPy Lab

Try it on paper first. A hint, the key idea and the worked solution are here when you need them.

A ship sends a pulse of ultrasound down. The echo from the sea floor comes back after $3.4\ \text{s}$ . How deep is the sea? (Speed of sound in sea water $1500\ \text{m/s}$ )

Need a reminder? The key ideaShow

An echo travels to the reflector and back: $d = \dfrac{vt}{2}$ . A separate echo needs at least $0.1\ \text{s}$ (a wall at least $17\ \text{m}$ away in air). SONAR uses ultrasound in sea water, about $1500\ \text{m/s}$ .

The worked solution

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Work it out on paper first. It is fine to get stuck or make a mistake: that is how we learn. When you are ready, compare your working with the solution.

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