What is the difference between transverse and plane waves?

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Discussion Overview

The discussion revolves around the differences between transverse waves and plane waves, with participants exploring definitions and clarifying concepts related to wave types. The scope includes theoretical understanding and conceptual clarification.

Discussion Character

  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • Some participants question whether all transverse waves are plane waves and vice versa, expressing confusion about the relationship between these terms.
  • One participant emphasizes the importance of defining what constitutes a plane wave and a transverse wave, suggesting that understanding these definitions is crucial for proper application.
  • Another participant provides an example of waves on the surface of water to illustrate the concept of transverse waves and how they relate to plane waves.
  • There is a discussion about the characteristics of longitudinal waves and whether they can be considered plane waves, with some participants asserting that they cannot.
  • Participants express uncertainty about the implications of wave phase and displacement direction, questioning how these relate to the definitions of plane and transverse waves.
  • One participant notes the practical challenges of producing true plane waves and suggests that spherical waves can be approximated as plane waves under certain conditions.

Areas of Agreement / Disagreement

Participants do not reach a consensus on the definitions and relationships between transverse waves and plane waves. Multiple competing views and uncertainties remain throughout the discussion.

Contextual Notes

Some participants indicate that definitions may be unclear or that their understanding is hindered by the explanations provided, suggesting a need for clearer communication of concepts.

dyn
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Hi.
Are all transverse waves plane waves ?
Are all plane waves transverse ?
I'm confused about the difference. I know the difference between transverse and longitudinal waves but I'm not sure on how plane waves fit into the picture ?
Thanks
 
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Rather than just telling you the answer I will ask you what defines a Plane wave and what defines a Transverse Wave (and also a Longitudinal Wave)?
Why, for instance, could you not expect to find a plane sound wave? These terms all have distinct meanings and their meanings tell you all about where they are appropriate to use.
 
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An answer would have been nice
 
dyn said:
An answer would have been nice
I think @sophiecentaur is just trying to get you to articulate what reading and research you have done so far. I think your questions in this thread are good ones -- it would just be good if you showed us what you have found so far. Thanks.
 
I know the definitions of transverse and longitudinal waves and understand them. I know the definition of plane waves ( waves whose surfaces of constant phase are infinite planes perpendicular to the direction of propagation ) but I don't really understand this definition as it just sounds like a transverse wave. Hence the question.
 
Think about waves in the surface of a body of water. These are transverse waves - they're propagating horizontally along the surface of the water while the water is waving up and down vertically. Draw a line along the crest of one wave and you have a surface of constant phase; it's a straight line extending out to infinity you have a plane wave (although it's a wave in the two dimensional surface of the water instead of three-dimensional space, so the surface of constant phase is a line instead of a plane).
 
dyn said:
I know the definitions of transverse and longitudinal waves and understand them. I know the definition of plane waves ( waves whose surfaces of constant phase are infinite planes perpendicular to the direction of propagation ) but I don't really understand this definition as it just sounds like a transverse wave. Hence the question.
I asked you the question rather than giving you a simple answer for a good reason. From your post here, you already know the answer if you ask yourself why a longitudinal wave should not have constant phase over a plane (i.e. what's so special about a transverse wave that only it can have constant phase over a plane?)
PS I often get shot down when I answer questions directly - in my enthusiasm to 'educate' - and someone will intervene with a 'question'. A chap can't win. :smile:
But the point is, have you a notion of the answer to your question now?
The wave equation
A = A0Sin(ωt-kx)
doesn't specify the direction of the displacement (polarisation or any vector direction)
 
Thanks for your replies but I'm still confused.
A longitudinal wave can not be a plane wave ?
A transverse wave on a string can not be a plane wave as there will not be a surface of constant phase only single points ?
Any transverse wave in 2-D or 3-D will be a plane wave as long as the surfaces of constant phase are infinite planes perpendicular to the direction of propagation eg an EM wave ?
 
dyn said:
Thanks for your replies but I'm still confused.
A longitudinal wave can not be a plane wave ?
A transverse wave on a string can not be a plane wave as there will not be a surface of constant phase only single points ?
Any transverse wave in 2-D or 3-D will be a plane wave as long as the surfaces of constant phase are infinite planes perpendicular to the direction of propagation eg an EM wave ?
If the phase of a wave is the same over a plane, it is a plane wave, what has the phase got to do with the direction of displacement of the oscillations? Have you been reading what has been written above in this thread? Perhaps you could tell us where you are finding contradictions. Are you using the right definitions for the terms? Did you look them up?
The practicality is that a true plane wave is hard to produce and it is best to start with a small ('point') source and let a spherical wave expand far enough to consider a part of that surface as being a plane. (The same as we treat the ground under our feet as flat, despite having a spherical Earth.)
 
  • #10
sophiecentaur said:
If the phase of a wave is the same over a plane, it is a plane wave, what has the phase got to do with the direction of displacement of the oscillations? Have you been reading what has been written above in this thread? Perhaps you could tell us where you are finding contradictions. Are you using the right definitions for the terms? Did you look them up?
The practicality is that a true plane wave is hard to produce and it is best to start with a small ('point') source and let a spherical wave expand far enough to consider a part of that surface as being a plane. (The same as we treat the ground under our feet as flat, despite having a spherical Earth.)

Yes I have been reading what has been written. That's the point of a forum. Have you ever considered that the fact that as I obviously don't understand this issue ,the problem might lie with the clarity of the advice given to me ?
 
  • #11
Thread closed temporarily for Moderation...
 
  • #12
Based on your previous post in a different thread, this thread will remain closed.
dyn said:
hi strangerep. If you don't want to answer my question that's up to you. I have a policy of only accepting help from people who wish to help me.
 
Last edited:

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