Harmonic Plane Wave: Form & Explanation

  • Context: Undergrad 
  • Thread starter Thread starter Tosh5457
  • Start date Start date
  • Tags Tags
    Harmonic Plane Wave
Click For Summary

Discussion Overview

The discussion centers around the mathematical form and explanation of harmonic plane waves, exploring their derivation, definitions, and characteristics. Participants engage with both theoretical and conceptual aspects of wave equations and their representations.

Discussion Character

  • Technical explanation
  • Conceptual clarification
  • Debate/contested

Main Points Raised

  • One participant asks about the specific form of the harmonic plane wave equation, highlighting the variables involved such as position vector, direction vector, wave velocity, and phase constant.
  • Another participant suggests that the form arises from solving the wave equation using Cartesian coordinates and the method of separation of variables, indicating a preference for this approach over spherical coordinates.
  • A different viewpoint emphasizes that any traveling wave can be expressed as a function of the form f(r·s - vt), asserting that harmonic functions must be sine or cosine.
  • Two participants seek clarification on the definition of a plane harmonic wave, with one providing a description that relates it to uniform displacement across a plane perpendicular to the wave's direction and its relation to spherical waves at a distance.
  • One participant notes that using spherical coordinates leads to spherical harmonics and Bessel functions, which diverges from the plane wave representation.

Areas of Agreement / Disagreement

Participants express differing views on the derivation methods and definitions of plane harmonic waves, indicating that multiple competing perspectives remain without a consensus.

Contextual Notes

The discussion includes assumptions about the coordinate systems used and the nature of wave functions, but these remain unresolved and depend on the context of the wave equations being discussed.

Tosh5457
Messages
130
Reaction score
28
Hi, why does the harmonic plane wave have the form below:

V(r,t)= acos[\omega (t-\frac{r\cdot s}{v})+\delta ]

(r is the position vector, s is the vector that points to the direction the wave is propagating, v is the wave propagation velocity and delta is the phase constant).
 
Physics news on Phys.org
it just comes out by solving the wave eqn
2v=∂t2v,where c=1 I have put.
You can use spherical coordinates to get it,but more simple would be cartesian coordinate and then using the method of separation of variables, you can get it.
 
More simply, any function that represents a traveling wave is a function of r.s-vt,ie f(r.s-vt)(r and s are vectors ofcourse). If a harmonic function travels as a wave,then the nature of the function is harmonic,ie sine or cosine.
 
what is the definition of a plane harmonic wave?
 
Using spherical coordinates gives you the spherical harmonics and spherical Bessel functions, not the plane wave. Separation in Cartesian coordinates gives plane waves.
 
Francessca said:
what is the definition of a plane harmonic wave?

It's just a posh way of describing a simple wave for which the displacement at any given time is the same over a plane (at right angles to the direction of propagation). It's the same expression as you get for a wave on a one dimensional string and is the limit for spherical wave at a great distance from the source. It's a very convenient approximation to use.
 

Similar threads

  • · Replies 3 ·
Replies
3
Views
2K
  • · Replies 1 ·
Replies
1
Views
2K
  • · Replies 2 ·
Replies
2
Views
2K
  • · Replies 1 ·
Replies
1
Views
1K
  • · Replies 8 ·
Replies
8
Views
2K
  • · Replies 10 ·
Replies
10
Views
2K
  • · Replies 3 ·
Replies
3
Views
2K
  • · Replies 8 ·
Replies
8
Views
3K
  • · Replies 4 ·
Replies
4
Views
1K
  • · Replies 4 ·
Replies
4
Views
2K