# Homework Help: Sound, pressure amplitude.

1. Feb 4, 2010

### Emir Kano

1. The problem statement, all variables and given/known data

Consider an ultrasound beam incident normal to a boundary between two media with the same density, but
where the speed of sound in the second medium is 50 percent larger than that in the first. Calculate the ratio
between the pressure amplitudes of the incident and reflected waves.

2. Relevant equations

Wave velocity c (ms-1) = wavelength λ (m) x frequency f (Hz)

p = βcv
p = presuure
β = density
c= speed
v= ? (speed as well ?

3. The attempt at a solution

Im confused as to what the c and v are in this case.

I have tried searching and some places are saying its speed squared.

Or have I got the wrong formula and its some derivation.

But Im lost. Is there enough info to answer the question ?

2. Feb 4, 2010

anyone ?

3. Feb 5, 2010

no one lol ?

4. Feb 5, 2010

### ideasrule

Fresnel equations?

5. Feb 5, 2010

### Emir Kano

I think Its not that its to do with the p = βcv

But I dont know what the 'c' and 'v' are. In this case do they both stand for speed. In which case the formula becomes p=βc^2. Or is it something completley different.