# What is the frequency of the signal?

1. Mar 30, 2009

### XodoX

1. A water wave has a speed of 1.0 m/s. The distance between crests is 0.5 m. What is the
wavenumber of the wave? If an observer at a fixed location measures the height h(t) of
the wave that passes by, what is the frequency of the signal h(t)?

2. k =2π/λ -> to get k= wavenumber

h (t) = Acos (ωt − kz +φ)

Hello, I need to do the above problem. I do have k( wavenumber). It's 12.56.

I can move on to the second question now. The equation I would use is the second one above.

ω = K*V.
T should be 0.
k is given now.

How do I get A and φ ? It should be φ = −ψ. But I don't know how to get −ψ.

ω could also be ω= 2πf But I don't know how to get f cause I don't have the Herz for the wave.

I hope somebody can help me!

Thank you!

Last edited: Mar 30, 2009
2. Mar 30, 2009

### Redbelly98

Staff Emeritus
Re: waves

What equation relates frequency, wavelength, and wave speed?

3. Mar 30, 2009

### XodoX

Re: waves

Sorry, I don't get what you're trying to tell me. A might be the 0.5? Originally , I thought z was the 0.5.

Last edited: Mar 30, 2009
4. Mar 30, 2009

### Redbelly98

Staff Emeritus
Re: waves

Forget A, that is the amplitude and is not needed here.

Your text book should have an equation containing f, λ, and v (frequency, wavelength, and wave speed, respectively). You are given λ and v in the problem statement, so the equation I refer to can be used to calculate what the frequency f is.

Again, you should be able to find it in your text book.

5. Mar 30, 2009

### XodoX

Re: waves

We don't have a text book. Just the notes provided by the teacher. And I tried every single equation, but I don't get it.

6. Mar 30, 2009

### Redbelly98

Staff Emeritus
7. Mar 30, 2009

### XodoX

Re: waves

Thank you! This one finally works:)