Register to reply

Why transverse wave cannot propagate in a gas or in liquid?

by sphyics
Tags: liquid, propagate, transverse, wave
Share this thread:
willem2
#2
Sep22-09, 02:22 PM
P: 1,398
How can a transverse wave propagate in a solid?
DaTario
#3
Sep22-09, 02:23 PM
P: 555
I think it is because particles in gas doesn't tend to memorize its height or its distance to some wall. In gas you should observe memory of (mean) relative distance between particles. Thus you may have longitudinal wave.
best regards

DaTario

sphyics
#4
Sep22-09, 02:31 PM
P: 103
Why transverse wave cannot propagate in a gas or in liquid?

here is hyperphysics link

http://hyperphysics.phy-astr.gsu.edu...nd/tralon.html

to quote it
Transverse waves cannot propagate in a gas or a liquid because there is no mechanism for driving motion perpendicular to the propagation of the wave.
wat does tis mean by ?
Bob_for_short
#5
Sep22-09, 02:33 PM
P: 1,160
Quote Quote by sphyics View Post
please do explain in detail.
In fact they can but they fade out very quickly. They are called viscosity waves.

Any wave dissipates with distance but the viscosity waves are weak (the coupling mechanism is weak) and the dissipation is too strong.
PeterDonis
#6
Sep24-09, 01:11 PM
Physics
Sci Advisor
PF Gold
P: 6,166
Quote Quote by sphyics View Post
wat does tis mean by ?
A transverse wave propagates in a solid because each atom of the solid has an "equilibrium location" where the forces on it from all its neighboring atoms balance. If one atom gets pulled out of its equilibrium location by a disturbance, it will tend to be pulled back to that location. However, when it's out of its equilibrium location it pulls its neighbors out of their equilibrium locations too, and so on down the line; the end result is that a transverse wave disturbance propagates through the material.

In fluids (liquids and gases), atoms have no "equilibrium location"; they can move freely past each other. So if one atom gets moved by a disturbance, there's no restoring force to pull it back to its equilibrium location, because there is no equilibrium location. Instead, as DaTario said, each atom is driven by the forces of neighboring atoms to maintain a given average distance between itself and its neighbors, but nothing else; so if one atom is disturbed, it will move to restore its average distance to its neighbors (and they will move in turn in response to the first one moving), but the atom won't be in the same place it was before when it's done equilibrating again. This allows longitudinal waves to propagate in fluids, but not transverse waves.
Dadface
#7
Sep24-09, 01:52 PM
PF Gold
Dadface's Avatar
P: 2,022
Are we discounting surface waves here eg the waves I produce when I throw a stone in a pond?
Bob_for_short
#8
Sep24-09, 01:58 PM
P: 1,160
Yes, we do. They are surface waves. They fade out with depth quickly.

As I said, the transversal waves in liquid are possible in theory and practice but they are extremely dissipating, not propagating far away.
sphyics
#9
Sep24-09, 04:28 PM
P: 103
Quote Quote by PeterDonis View Post
A transverse wave propagates in a solid because each atom of the solid has an "equilibrium location" where the forces on it from all its neighboring atoms balance. If one atom gets pulled out of its equilibrium location by a disturbance, it will tend to be pulled back to that location. However, when it's out of its equilibrium location it pulls its neighbors out of their equilibrium locations too, and so on down the line; the end result is that a transverse wave disturbance propagates through the material.

In fluids (liquids and gases), atoms have no "equilibrium location"; they can move freely past each other. So if one atom gets moved by a disturbance, there's no restoring force to pull it back to its equilibrium location, because there is no equilibrium location. Instead, as DaTario said, each atom is driven by the forces of neighboring atoms to maintain a given average distance between itself and its neighbors, but nothing else; so if one atom is disturbed, it will move to restore its average distance to its neighbors (and they will move in turn in response to the first one moving), but the atom won't be in the same place it was before when it's done equilibrating again. This allows longitudinal waves to propagate in fluids, but not transverse waves.
thats indeed a great explanation :)


Register to reply

Related Discussions
Time needed for a transverse wave to propagate on a string Introductory Physics Homework 3
Time for a wave to propagate Introductory Physics Homework 1
Transverse wave Introductory Physics Homework 0
Wave equation, transverse wave Introductory Physics Homework 3
Difference between people 'doing the wave', and a transverse wave? Introductory Physics Homework 11