# Conceptual question about longitudinal waves

Tags: conceptual, longitudinal, waves
 P: 3,016 So we are working on sound waves in my physics course now and I was doing some textbook reading. I have been following it pretty well, but I just came across a relationship that I am not quite following. It is with reference to wave interference. Let us say that two sound waves are emitted from two different point sources $$S_1$$ and $$S_2$$. The waves have the same wavelength $$\lambda$$ and are in phase at their sources. They take paths of lengths $$L_1$$ and $$L_2$$ and pass through point P. The text says that their phase difference $$\phi$$ is dependent on $$\Delta L=|L_1-L_2|$$ Thus to relate the variables $$\Delta L$$ and $$\phi$$ we can use the proportion: $$\frac{\phi}{2\pi}=\frac{\Delta L}{\lambda}$$ I know that I should see it, but I don't exactly follow this proportion. Could somebody ellaborate on this a little for me? I sure would appreciate, Casey
Ah. I see that now. Thanks LP. It makes even more sense now that I wrote out what you did^^^...the phase difference is $$\phi$$