# I Wave Speed

1. Feb 24, 2017

### Theudius

Hi could someone please explain to me what is meant by the term wave speed because I am confused by the definition which states "how fast a point moves on the wave".

Last edited: Feb 24, 2017
2. Feb 24, 2017

### Staff: Mentor

Welcome to the PF.

Are you familiar with the difference between the "phase velocity" and the "group velocity" in a wave? Have you read about this at Wikipedia yet? That might be a good start -- you could post links to the parts of the explanation that you aren't understanding yet.

3. Feb 24, 2017

### Staff: Mentor

BTW, that quote can imply other things as well.

The topics I mentioned in my last reply (phase velocity and group veloticy) have to do with how fast the crests of a wave move forward. But "how fast a point on the wave moves" can also imply how fast a point on a transverse wave moves "up and down" as the wave moves "left to right".

So in your reading about waves, also include some reading about "transverse waves" and "longitudinal waves". You will start to see how the quote you posted is not really defined well enough to give you a good answer without more context and details.

4. Feb 24, 2017

### rootone

5. Feb 25, 2017

### Theudius

Hi thanks for your replies, I have been reading further into waves and I'm starting to understand the term wave speed in more detail.

I have also started reading into interference and path difference but one thing i'm uncertain about is how it is related to wavelengths and how the formulae path difference = nλ and path difference = (n+ 1/2)λ are derived.