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

1. May 11, 2008

### looi76

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

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

2. Relevant equations
$$x = \frac{d\lambda}{a}$$

$$v = f\lambda$$

3. 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: May 11, 2008
2. May 11, 2008

### Kurdt

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

3. May 11, 2008

### Antenna Guy

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

Regards,

Bill

4. May 11, 2008

### Kurdt

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

5. May 12, 2008

### looi76

So, the answer is = 0.68m by 360° ?

6. May 12, 2008

### Gib Z

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 =]

7. May 12, 2008

### Antenna Guy

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

8. May 12, 2008

### Kurdt

Staff Emeritus
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).

9. May 12, 2008

### looi76

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

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

$$x = 90^o$$

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

10. May 12, 2008

### Kurdt

Staff Emeritus
Thats correct.