# What is its period in the water?

1. May 17, 2006

### aerogurl2

i need some help on this problem:
A sonar signal of frequency 1.00x10^6 Hz has a wavelength of 1.50mm in water.

a) What is its period in the water?
b)What is its period in the air?

Can someone guide me through the steps in order to arrive to the solution or explain to me how to solve this? Thanx

2. May 17, 2006

### nrqed

What is the definition of period? It is simply one over the frequency.
When a wave changes medium (water to air) does the frequency change?

3. May 17, 2006

### aerogurl2

the medium doesn't travel with the wave so it wouldn't effect the period is that right? so the period for both water and the air would be the same?

4. May 17, 2006

### nrqed

Your conclusion is correct but it's not because the medium does not travel with the wave. When a wave changes medium, its speed *and* its wavelength changes but the frequency does not change (it is ultimately connected to conservation of energy but you should not worry about that).

Patrick

5. May 17, 2006

### aerogurl2

oki thanx for your help Patrick

6. May 17, 2006

### nrqed

You are most welcome. And best luck!