Standing waves on a string -- Find the difference of phases

[LCSphysicist]

Homework Statement

I will post below.

Relevant Equations

I am not sure, since i am wrong with my equation.

The immediate thing i did here is
$\Delta \varphi = k(\Delta x)$
Interesting enough for a topic, if you use this equation you end up wrong like me, the answer is not D.
Not sure what is the problem.

 

[TSny]

Consider a section of the string between two nodes. Consider any two points of the string in this section. How would you describe the phase difference of the motion of these two points?

 

[LCSphysicist]

Consider a section of the string between two nodes. Consider any two points of the string in this section. How would you describe the phase difference of the motion of these two points?

The nodes are spaced by a half of the wavelength, that is, pi rad?
As the equation implies:
$$ k\Delta x = \frac{2\pi }{\lambda }*\frac{\lambda }{2} $$
In this case the equation work :/

 

[TSny]

Identify two consecutive nodes in the following animation. Pick any two points of the string lying between these two nodes. What can you say about the phase difference of the motion of the two points?

https://en.wikipedia.org/wiki/Standing_wave#/media/File:Standing_wave.gif

 

[LCSphysicist]

Identify two consecutive nodes in the following animation. Pick any two points of the string lying between these two nodes. What can you say about the phase difference of the motion of the two points?

https://en.wikipedia.org/wiki/Standing_wave#/media/File:Standing_wave.gif

Wow, now i get... the difference if pi...
I think i was applying equation of traveling wave for standing waves, right?

 

[TSny]

Wow, now i get... the difference if pi...

Good.

I think i was applying equation of traveling wave for standing waves, right?

Yes.