Group velocity and phase velocity

Click For Summary
SUMMARY

The group velocity is defined as the velocity at which the envelope of a wave travels, mathematically expressed as group velocity = dw/dk. This derivation is an approximation that holds true under specific conditions, particularly when the amplitude function A(k) is sharply peaked. In cases where A(k) is not sharply peaked, higher-order terms of the phase must be considered, leading to modifications in the pulse shape, commonly referred to as "chirping." The discussion highlights a potential misunderstanding regarding the application of this approximation in wavefunction analysis.

PREREQUISITES
  • Understanding of wave mechanics and wavefunctions
  • Familiarity with the concepts of group velocity and phase velocity
  • Knowledge of linearization techniques in mathematical physics
  • Basic grasp of Fourier analysis and its applications in wave theory
NEXT STEPS
  • Study the derivation of group velocity in the context of wave packets
  • Explore the effects of higher-order terms in wavefunction analysis
  • Learn about the phenomenon of "chirping" in waveforms
  • Investigate the implications of wavefunction behavior near delta functions
USEFUL FOR

Students and professionals in physics, particularly those focused on wave mechanics, as well as researchers exploring wavefunction behavior and its applications in various fields of science and engineering.

Naman Jain Kota
Messages
12
Reaction score
0
Could you please explain the derivation of
group velocity = dw/dk

I read ut here https://en.m.wikipedia.org/wiki/Group_velocity

Is it approximation, if so under what circumstances
 
Physics news on Phys.org
Isn't the derivation already available in that link? The group velocity is defined to be the velocity at which the envelope of a wave travels. It's an approximation in the sense that it was derived involving approximating the phase in first order of ##k##.
 
How did they put the linearization equation?
Was there approximate and then it could really be applied for wavefunction approaching delta functions
 
Yes, the linearization is an approximation which only applies to cases where ##A(k)## is sharply peaked. If this is not the case, higher orders of the phase must be included in the calculation and they usually lead to the modification of the shape of the pulse (so-called "chirping").
 
  • Like
Likes   Reactions: Naman Jain Kota
If i add two sine wave functions (real parts) envelopes are formed. So group velocity must not be dw/dk. Asking coz my proff said that which i feel is wrong
 

Similar threads

  • · Replies 2 ·
Replies
2
Views
2K
  • · Replies 14 ·
Replies
14
Views
4K
  • · Replies 18 ·
Replies
18
Views
5K
  • · Replies 3 ·
Replies
3
Views
2K
  • · Replies 4 ·
Replies
4
Views
2K
Replies
6
Views
2K
  • · Replies 2 ·
Replies
2
Views
5K
  • · Replies 2 ·
Replies
2
Views
2K
  • · Replies 1 ·
Replies
1
Views
1K
  • · Replies 1 ·
Replies
1
Views
2K