Solving Stationary Waves Homework Problems

[ibysaiyan]

Homework Statement

A primitive question yet I can't am having difficulty in solving it.
http://img524.imageshack.us/i/confusedu.png"

Homework Equations

F = 1/T

The Attempt at a Solution

The only value given is the difference in the time frame of the respective waves.The only other thing I could pick out of this question is the difference in the phases of both waves.
So i thought of doing ti this way:
Let "X" be the time period of one wave.By doing so:
X/0.1 = 2pi/pi *Pi : Since the bottom wave is in antiphase to the top one by 180 degree ?:s
Am I on the right track ? Thanks for your help in advance.

 

[cepheid]

From one flash to the next (a time period of 0.1 s), the point P on the rope goes from being at a trough to being a crest (in the wave). Therefore, what is the smallest number of periods that could have elapsed in that 0.1 s? Is it a full period? Half a period?

Based on the answer to my question above, what is the longest possible period for the wave? How are the other possible periods related to this one? (Hint: they should be integer fractions of it, and the thing that differentiates them from each other is how many oscillations the waves goes through in between illuminations).

 

[ibysaiyan]

From one flash to the next (a time period of 0.1 s), the point P on the rope goes from being at a trough to being a crest (in the wave). Therefore, what is the smallest number of periods that could have elapsed in that 0.1 s? Is it a full period? Half a period?

Based on the answer to my question above, what is the longest possible period for the wave? How are the other possible periods related to this one? (Hint: they should be integer fractions of it, and the thing that differentiates them from each other is how many oscillations the waves goes through in between illuminations).

Will the smallest no. of periods be half ?
Err Sorry but I still don't get it.Could this question be solved in terms of phase difference ? :s

 

[ibysaiyan]

Anyone ?

 

[cepheid]

Will the smallest no. of periods be half ?

Yes, because the shortest way to go from a trough to a crest is to experience half of an oscillation. Do you understand? A full oscillation would be to go from trough to crest and then back to trough again.

So, we have concluded that one possibility is that the 0.1 s interval between flashes corresponded to half of the period of oscillation of the wave. Call the period "T".

0.1 s = 0.5*T

So right there, you have one possible value for the period of the wave. Sorry for the delay in responding.