# waves

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#1
struggling to understand 4 part 2

https://www.ocr.org.uk/Images/319537...nd-photons.pdf

in 1) the mark scheme says that all the points have the same amplitude. but how is this true for point R as the amplitude is 0?

in 2) how do i know that they all have different phases?

Thanks
0
1 year ago
#2
(Original post by fiftythree)
struggling to understand 4 part 2

https://www.ocr.org.uk/Images/319537...nd-photons.pdf

in 1) the mark scheme says that all the points have the same amplitude. but how is this true for point R as the amplitude is 0?

in 2) how do i know that they all have different phases?

Thanks
hey, I think 1) it might be because the question states 'the motion of points P, Q, R and S'. The diagram is showing a section at one instant of time. Because the wave is a progressive one, all the points will move with the same amplitude when the wave moves through it. Like water waves. If someone is in front of you, they will rise to the same height you do as the wave passes through the water. So P Q R and S will all 'rise' to the same amplitude as the wave passes through the medium

You're right in that R will not have the same amplitude - but that'll be true for a standing wave.

2) they're in different phases because they're not on the same point of the oscillation. i.e. one is on a crest and other is on a crest. They're all in different places, so they're in different phases

hope that makes sense

2)
0
1 year ago
#3
(Original post by fiftythree)
...
Your point doesn't make sense, they all have different y-coords at this time, what's special about R at y = 0?

All points oscillate vert with equal freq and amp; their phases must differ since y-coords differ at this time.
Last edited by Physics Enemy; 1 year ago
0
#4
(Original post by violetmari12)
hey, I think 1) it might be because the question states 'the motion of points P, Q, R and S'. The diagram is showing a section at one instant of time. Because the wave is a progressive one, all the points will move with the same amplitude when the wave moves through it. Like water waves. If someone is in front of you, they will rise to the same height you do as the wave passes through the water. So P Q R and S will all 'rise' to the same amplitude as the wave passes through the medium

You're right in that R will not have the same amplitude - but that'll be true for a standing wave.

2) they're in different phases because they're not on the same point of the oscillation. i.e. one is on a crest and other is on a crest. They're all in different places, so they're in different phases

hope that makes sense

2)
ty
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