# What is the phase difference between the motions of two points on the wave

[SOLVED] What is the phase difference between the motions of two points on the wave..

## Homework Statement

The frequency of a certain wave is $$500Hz$$ and its speed is $$340ms^{-1}$$.What is the phase difference between the motions of two points on the wave $$0.17cm$$ apart?

## Homework Equations

$$x = \frac{d\lambda}{a}$$

$$v = f\lambda$$

## The Attempt at a Solution

$$f = 500Hz \ \ \ v = 340ms^{-1} \ \ \ a = 0.17 \times 10^{-2} cm$$

$$v = f\lambda$$

$$\lambda = \frac{v}{f} = \frac{340}{500} = 0.68m$$

What should I do next?

Last edited:

## Answers and Replies

Kurdt
Staff Emeritus
Gold Member
Two points 0.68cm apart will be out of phase by 360 degrees.

Two points 0.68cm apart will be out of phase by 360 degrees.
Two points $\lambda$ apart will be out of phase by 360 deg.

Regards,

Bill

Kurdt
Staff Emeritus
Gold Member
In this case that is 0.68m. Damn I just realised I said cm, but you know what I mean. :tongue:

So, the answer is = 0.68m by 360° ?

Gib Z
Homework Helper
No, I won't be. You know the phase difference between points 0.68m apart is 360°, the question asks the phase difference for 0.17m, which happens to be a quarter the quantity of which we do know the phase difference for. Just one more step =]

So, the answer is = 0.68m by 360° ?
Define the terms in your first relevant equation - one of those terms should be what you solve for to get the answer.

BTW - check what you wrote for "a" (cm?).

Regards,

Bill

Kurdt
Staff Emeritus
Gold Member
So, the answer is = 0.68m by 360° ?
As GibZ alluded to, I was trying to coax you toward the right answer not just give you the answer outright (since that would be against forum policy).

$$0.68m = 360^o$$
$$0.17m = x$$

$$x = \frac{0.17 \times 360}{0.68}$$

$$x = 90^o$$

So, the phase difference is $$90^o$$ ?

Kurdt
Staff Emeritus