Why Is Infinite Velocity Characteristic of Diffusion Processes?

[fisico30]

Hello everyone,

a wave propagates at a speed (group of phase speed), less than the speed of light, no matter what type of wave we are dealing with (electromagnetic, mechanical,...).

Why is infinite velocity characteristic of a diffusion process? What does that mean?
For something to diffuse it always take some finite amount of time..


thanks!

 

[Mapes]

The diffusion model assumes infinite propagation speed to make the equations easier. In practice, the propagation speed is usually much faster than the diffusion speed (though not infinite), so the idealization works pretty well. Consider heat conduction through a metal: the diffusion speed might be on the order of mm/s, while the propagation speed is related to the speed of sound, which may be >100 m/s.

 

[charng]

Hello there! I can explain the difference between wave propagation and diffusion.

First, let's define what these terms mean. Wave propagation refers to the movement of a wave through a medium, such as air or water. This can be seen in everyday examples such as sound waves traveling through air or ocean waves moving across the surface of water.

On the other hand, diffusion is the process by which particles or molecules move from an area of high concentration to an area of low concentration. This can be seen in processes like gas diffusion in the air or the diffusion of molecules in a liquid.

Now, to answer your question about the difference in velocity between wave propagation and diffusion. The key factor here is the speed of the wave or particles involved. Waves, regardless of their type, always propagate at a finite speed, which is usually slower than the speed of light. This means that there is a limit to how fast a wave can travel through a medium.

However, in diffusion, there is no set speed for the particles or molecules to move. They can move at any speed, including infinite velocity. This is because diffusion is a random process and the speed of individual particles can vary greatly. So while it may seem counterintuitive, infinite velocity is characteristic of diffusion because there is no set speed limit for the movement of particles.

In summary, wave propagation and diffusion are two distinct processes with different characteristics, including the speed at which they occur. I hope this explanation helps clarify the difference between these two concepts. Keep exploring and asking questions!