Turn on thread page Beta
    • Thread Starter
    Offline

    5
    ReputationRep:
    Are the transmitted and the reflected waves always in phase when they are at antinodes; and are always in antiphase when at nodes? Or is it the other way round? I don't understand why though. I don't get how standing waves can be in phase and in antiphase.
    Offline

    15
    ReputationRep:
    A stationary wave is a wave such that two waves with the same amplitude and frequency travelling in opposite directions meet and essentially counteract by kinda cancelling the other about.

    By this I mean the net displacement away from the imaginary horizontal line through the centre of the resulting wave forme is 0 at all parts of the wave.
    This would mean that if an antinode has a displacement (amplitude) of +3 away from the horizontal line then that would need to be counteracted by a wave with a displacement of -3 as you always add the displacements of the two waves meeting. This will result in an overall horizontal line on top of your existing imaginary line.

    A node is a point in a wave where your amplitude is 0, so where it crosses your horizontal line.

    An antinode is a point on a wave where the amplitude is at it's maximum.

    Node:
    'At these points, the two waves add with opposite phase and cancel each other out. They occur at intervals of half a wavelength (λ/2). Midway between each pair of nodes are locations where the amplitude is maximum. These are called the antinodes.'
    • Thread Starter
    Offline

    5
    ReputationRep:
    (Original post by S.H.Rahman)
    A stationary wave is a wave such that two waves with the same amplitude and frequency travelling in opposite directions meet and essentially counteract by kinda cancelling the other about.

    By this I mean the net displacement away from the imaginary horizontal line through the centre of the resulting wave forme is 0 at all parts of the wave.
    This would mean that if an antinode has a displacement (amplitude) of +3 away from the horizontal line then that would need to be counteracted by a wave with a displacement of -3 as you always add the displacements of the two waves meeting. This will result in an overall horizontal line on top of your existing imaginary line.

    A node is a point in a wave where your amplitude is 0, so where it crosses your horizontal line.

    An antinode is a point on a wave where the amplitude is at it's maximum.

    Node:
    'At these points, the two waves add with opposite phase and cancel each other out. They occur at intervals of half a wavelength (λ/2). Midway between each pair of nodes are locations where the amplitude is maximum. These are called the antinodes.'
    So the transmitted and the reflected waves must be in phase at antinodes, and in antiphase at nodes?
    Offline

    15
    ReputationRep:
    (Original post by Kaelyn327)
    So the transmitted and the reflected waves must be in phase at antinodes, and in antiphase at nodes?
    Sorry if I've confused you.

    They are at antiphase or completely out of phase at nodes but are in phase at antinodes.

    'The two waves are not "in antiphase" (constantly, that is) and they do cancel each other out. They cancel out at the nodes (antiphase) but reinforce at the antinodes where they are in phase. You do always get a standing wave in this case if the waves have the same frequency (and thus same wavelength).'
    • Thread Starter
    Offline

    5
    ReputationRep:
    (Original post by S.H.Rahman)
    Sorry if I've confused you.

    They are at antiphase or completely out of phase at nodes but are in phase at antinodes.

    'The two waves are not "in antiphase" (constantly, that is) and they do cancel each other out. They cancel out at the nodes (antiphase) but reinforce at the antinodes where they are in phase. You do always get a standing wave in this case if the waves have the same frequency (and thus same wavelength).'
    Nah, it's fine. So you know most stationary waves diagrams in textbooks, they have one solid and one dotted line to show the waves and nodes. Is it just a visual image of both incoming and reflected wave combined together? So it's not showing how the transmitted and reflected waves should look like separately?
    So if the two waves are in phase, they interference constructively, and thus results in bigger crest and bigger trough, and so antinodes are formed in the combined visual image. (?)
    And if the two waves are in antiphase, they interference destructively, which means they cancel out each other and results in nodes in the combined image. (?)
    Offline

    15
    ReputationRep:
    (Original post by Kaelyn327)
    Nah, it's fine. So you know most stationary waves diagrams in textbooks, they have one solid and one dotted line to show the waves and nodes. Is it just a visual image of both incoming and reflected wave combined together? So it's not showing how the transmitted and reflected waves should look like separately?
    So if the two waves are in phase, they interference constructively, and thus results in bigger crest and bigger trough, and so antinodes are formed in the combined visual image. (?)
    And if the two waves are in antiphase, they interference destructively, which means they cancel out each other and results in nodes in the combined image. (?)
    Could I see this picture?
    • Thread Starter
    Offline

    5
    ReputationRep:
    Name:  image.jpg
Views: 61
Size:  502.8 KB
    (Original post by S.H.Rahman)
    Could I see this picture?
    Offline

    15
    ReputationRep:
    I've confused myself now argh D: Someone else plz come help?! lol
    Offline

    12
    ReputationRep:
    http://www.walter-fendt.de/html5/phe...lection_en.htm

    This website shows how standing waves work well imo
    Offline

    12
    ReputationRep:
    Basically as both waves are traveling in opposite directions there can be a moment where they are completly in phase and a moment where they are completly out of phase
 
 
 
Reply
Submit reply
Turn on thread page Beta
Updated: November 7, 2017

University open days

  • University of Exeter
    Undergraduate Open Days - Exeter Campus Undergraduate
    Wed, 24 Oct '18
  • University of Bradford
    Faculty of Health Studies Postgraduate
    Wed, 24 Oct '18
  • Northumbria University
    All faculties Undergraduate
    Wed, 24 Oct '18
Poll
Who do you think it's more helpful to talk about mental health with?

The Student Room, Get Revising and Marked by Teachers are trading names of The Student Room Group Ltd.

Register Number: 04666380 (England and Wales), VAT No. 806 8067 22 Registered Office: International House, Queens Road, Brighton, BN1 3XE

Write a reply...
Reply
Hide
Reputation gems: You get these gems as you gain rep from other members for making good contributions and giving helpful advice.