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

1. Sep 22, 2009

### sphyics

2. Sep 22, 2009

### willem2

How can a transverse wave propagate in a solid?

3. Sep 22, 2009

### DaTario

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

4. Sep 22, 2009

### sphyics

5. Sep 22, 2009

### Bob_for_short

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.

6. Sep 24, 2009

### Staff: Mentor

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.

7. Sep 24, 2009

Are we discounting surface waves here eg the waves I produce when I throw a stone in a pond?

8. Sep 24, 2009

### Bob_for_short

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.

9. Sep 24, 2009

### sphyics

thats indeed a great explanation :)