Kaelyn327
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How to find the phase difference of two waves if they look like they are in phase but they have different displacement?
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Shaanv
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(Original post by Kaelyn327)
How to find the phase difference of two waves if they look like they are in phase but they have different displacement?
Post a picture please, the way ur question is worded is confusing.

Do u mean different amplitudes instead of displacement?

If the amplitude and frequency of the two waves are the same, but they have different displacements at the same time they are not in phase.
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Kaelyn327
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Yup I meant they have different amplitude but I thought they had different displacement as well.
What's the difference between amplitude and displacement? I know displacement can be either positive or negative depending on the graph whereas amplitude can not be negative.
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Shaanv
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(Original post by Kaelyn327)
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Yup I meant they have different amplitude but I thought they had different displacement as well.
What's the difference between amplitude and displacement? I know displacement can be either positive or negative depending on the graph whereas amplitude can not be negative.
Amplitude is the maximum displacement from equilibrium.

The two waves are in phase so the phase difference is zero, the amplitude doesnt affect phase difference, it only effects the ‘resultant wave’. There is also another solution which is valid for this question but ill let u figure that one out.

If anything was unclear feel free to quite me and ask a question. Also a friendly tip, always post a picture where u can, it helps immensely.
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Kaelyn327
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(Original post by Shaanv)
Amplitude is the maximum displacement from equilibrium.

The two waves are in phase so the phase difference is zero, the amplitude doesnt affect phase difference, it only effects the ‘resultant wave’. There is also another solution which is valid for this question but ill let u figure that one out.

If anything was unclear feel free to quite me and ask a question. Also a friendly tip, always post a picture where u can, it helps immensely.
Oh thank you so so much.
Let me try to rephrase the whole thing again to see if I really get it or not.
So amplitude is the maximum displacement from equilibrium position and it doesn't affect the phase difference. The two waves have different amplitudes but we can't say they have different displacements. Though the two waves have different amplitudes they are in phase. So phase difference is zero.
In phase, which also means
Phase difference in degrees = 360 degrees
Phase difference in radian = 2π rad
Because they could be 1λ away.
So as the question asks for answers in fractions of wavelength and degrees, I can say 0 λ and 0 degree, and / or, 1 λ and 360 degrees. (Am I right?)
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Shaanv
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(Original post by Kaelyn327)
The two waves have different amplitudes but we can't say they have different displacements.
I dont really like this wording. Other than that it was all fine.

They have different amplitudes, amplitude is maximum displacement, so there maximum displacements are different.

I think the axis on your graph are slightly confusing. The position axis is essentially a time axis, as u can see the waves have the same time period.

As both waves start at equilibrium at the same ‘time’ and have the same wavelength, they will be in phase and they will constructively interfere with each other.
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Kaelyn327
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(Original post by Shaanv)
I dont really like this wording. Other than that it was all fine.

They have different amplitudes, amplitude is maximum displacement, so there maximum displacements are different.

I think the axis on your graph are slightly confusing. The position axis is essentially a time axis, as u can see the waves have the same time period.

As both waves start at equilibrium at the same ‘time’ and have the same wavelength, they will be in phase and they will constructively interfere with each other.
Right, so if the position axis is a time axis, the phase difference in wavelength is genuinely the "time lag" of two waves(?), which makes more sense to me.
So as the superposition is the vector sum of the displacement of the two waves (and as they are in phase they will constructively interfere with each other, as you said) the superposition should look like supercrest supertrough and supercrest. (?)
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Shaanv
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(Original post by Kaelyn327)
Right, so if the position axis is a time axis, the phase difference in wavelength is genuinely the "time lag" of two waves(?), which makes more sense to me.
So as the superposition is the vector sum of the displacement of the two waves (and as they are in phase they will constructively interfere with each other, as you said) the superposition should look like supercrest supertrough and supercrest. (?)
Yep where u have a crest now, u will have a supercrest when they interfere, same goes for troughs
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Kaelyn327
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(Original post by Shaanv)
Yep where u have a crest now, u will have a supercrest when they interfere, same goes for troughs
I get it now
Thank you so so much x
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Shaanv
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(Original post by Kaelyn327)
I get it now
Thank you so so much x
No worries👊🏾💪🏾👌🏾 Ÿ™ðŸ¾
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